The authors apply non-linear spin wave theory to the problem of anisotropic spin-S Heisenberg models on the Kagome lattice. They argue that the non-linear terms of the analysis lead to two unusual effects: 1) the presence of a quantum phase transition as a function of the anisotropy parameter between $q=0$ and $\sqrt{3}\times \sqrt{3}$ order (whereas thermal fluctuations favor the $\sqrt{3}\times \sqrt{3}$ order regardless of the strength of the anisotropy) and 2) strong quantum effects in the spectral features that are not suppressed with $1/S$ as is typical.

[Phys. Rev. B 92, 144415] Published Tue Oct 13, 2015

]]>Magnetic force measurements are used to measure the penetration depth and pinning forces for vortices in the superconductor NdFeAsO${}_{1-x}$F${}_{x}$.

[Phys. Rev. B 92, 134509] Published Mon Oct 12, 2015

]]>The use of terahertz time-resolved studies in conducting and superconducting systems is gaining considerable interest, especially in the light of recent studies demonstrating induction of superconductivity in various materials with optical impulsive excitation. The authors carry out a theoretical analysis of the response functions typically measured by terahertz time-domain spectroscopy (THz-TDS) in metallic and superconducting samples. Within the Drude model, the authors found that THz-TDS does not simply measure the instantaneous conductivity change, in agreement with previous reports. They identify limits wherein the time-resolved THz-TDS spectrum does and does not approach the instantaneous conductivity change. They further show that the difference between the THz-TDS response and the instantaneous conductivity is largest when the photo-induced state changes from a normal metal to a superconductor.

[Phys. Rev. B 92, 134507] Published Fri Oct 09, 2015

]]>A fundamental question for understanding the decoherence of quantum spin qubits interacting with a bath of spins in the environment is the nature of the noise affecting the qubit - can it be modeled as classical noise or are quantum effects important? Here the authors experimentally demonstrate that in the favorable case of bismuth electron spin donors in silicon near values of a magnetic field known as clock transitions, the nuclear spin noise can be approximated as classical Gaussian noise. This finding is expected to influence efforts to optimize the control of qubits in silicon based quantum computation.

[Phys. Rev. B 92, 161403(R)] Published Thu Oct 08, 2015

]]>Previous studies have shown that the nuclear spin polarization in GaAs is spatially inhomogeneous. The authors of this paper argue that the hyperfine interaction between the electron spins and inhomogeneous nuclear field is of Dyakonov-Perel type. They show that the inclusion of corresponding anisotropic spin relaxation mechanism produces a better fit of the experimentally measured Hanle effect.

[Phys. Rev. B 92, 140201(R)] Published Wed Oct 07, 2015

]]>Anomalies in transport and thermodynamic quantities near a quantum critical point in the heavy fermion compound YbRh${}_{2}$Si${}_{2}$ are shown to be caused by the onset of spin-flip scattering above a certain crossover line in the T-H phase diagram.

[Phys. Rev. B 92, 155111] Published Wed Oct 07, 2015

]]>WTe${}_{2}$ has recently been reported to exhibit extremely large magnetoresistance, which may find potential applications in devices such as highly sensitive magnetic sensors and hard drives. In this paper, using ultrafast optical spectroscopy, the authors track the relaxation of photoexcited carriers in the time domain as they return to equilibrium in WTe${}_{2}$. Their experimental results not only resolve the time scales that ultimately limit potential applications of this material in electronic devices, e.g., high-speed hard drives, but also shed new light on the mechanisms governing the extremely large magnetoresistance.

[Phys. Rev. B 92, 161104(R)] Published Wed Oct 07, 2015

]]>The authors investigate the magnetothermoelectrical properties of an individual magnetic domain wall in a permalloy nanowire. They show that the thermopower contribution of a domain wall in a magnetic nanowire provides a underlying coupling of the magnetic structure and overall thermoelectric fingerprint. The observation of a domain wall magneto-Seebeck effect is further explained through a magnetization-dependent Seebeck coefficient of permalloy in combination with the local spin configuration of the domain wall.

[Phys. Rev. B 92, 140405(R)] Published Tue Oct 06, 2015

]]>The authors investigate the application of an “impurity” or inhomogeneous dynamical mean-field theory (DMFT) to two magnetic impurities on the surface of a 3D cubic lattice and coupled quantum dots. This work also compares the combination of a local self-energy with self consistency, which produces dramatically nontrivial results, with the exact solutions provided by the numerical renormalization group (NRG). Furthermore, the authors provide the limits where the local self-energy fails.

[Phys. Rev. B 92, 155101] Published Thu Oct 01, 2015

]]>The authors present evidence of many-body localization in a translationally invariant model Hamiltonian. The model, Ising-like, arises in the study of quantum glasses. The authors show that this model exhibits two regimes: one of fast relaxation and one of slow relaxation with dynamical features typically associated with many-body localized phases.

[Phys. Rev. B 92, 100305(R)] Published Mon Sep 28, 2015

]]>Motivated by a deeper understanding of strongly interacting topological phases and fractional Chern insulators the authors propose a formulation of a discretized Chern-Simon theory on random lattices and graphs.

[Phys. Rev. B 92, 115148] Published Mon Sep 28, 2015

]]>The authors demonstrate a means to determine the strength of excitonic correlations (as measured by the photoluminescence energy shift) of indirect excitons in semiconductor quantum wells. Because this energy shift is determined by how the excitons respond to an external potential, the authors apply an electrostatic periodic potential to the excitonic gas. By measuring the corresponding excitonic response due to this applied potential, they, using a complementary theory, are able to deduce the strength of correlations.

[Phys. Rev. B 92, 115311] Published Mon Sep 28, 2015

]]>It is generally expected that Majorana qubits are immune to decoherence at the hardware level for topological reasons. The authors investigate this question in detail and show that this is not true in a specific, widely studied, quantum computing architecture.

[Phys. Rev. B 92, 115441] Published Fri Sep 25, 2015

]]>This paper reports on successful application of electron energy loss spectroscopy (EELS) for probing low-energy electronic excitations at all values of momentum transfer with atomic-scale spatial resolution. In this regard EELS appears to be complementary to optical spectroscopy which probes only direct excitations with limited spatial resolution. The authors suggest that EELS can be used to study atomic-scale structural, electronic, magnetic and vibrational properties of systems having defects and impurities as well.

[Phys. Rev. B 92, 125147] Published Fri Sep 25, 2015

]]>The authors present an experimental mechanism for converting the state of a spin qubit in a quantum dot device into different charge states. This mechanism depends on metastable charge states present when the device has very asymmetric couplings to the external leads. This approach is used to observe Landau-Zener-Stuckelberg oscillations of the (S-${T}_{+}$) qubit.

[Phys. Rev. B 92, 125434] Published Fri Sep 25, 2015

]]>The non-equilibrium Anderson impurity model is solved to an unprecedented accuracy to obtain its spectral properties in the steady state using a recently developed approach.

[Phys. Rev. B 92, 125145] Published Thu Sep 24, 2015

]]>The authors theoretically study optical transitions in transition-metal dichalcogenides. In particular, they explain the difference between the excitonic properties of monolayer MoSe${}_{2}$ and WSe${}_{2}$. Excitons in WSe${}_{2}$ are thought to be bound to impurities. An alternative theory presented in this paper suggests that these excitons correspond to low-energy optical transitions. The authors also put forward an alternative explanation as to why the excitons in MoSe${}_{2}$ have vanishing polarization. They attribute this phenomenon to polaron-induced Rabi oscillations between dark and bright excitons.

[Phys. Rev. B 92, 125431] Published Wed Sep 23, 2015

]]>When a wave is incident on an open random medium it is decomposed into a number of “partial waves” that propagate independently along natural channels, the so-called transmission eigenchannels, and are superposed again when they leave the medium. Here, the authors propose the use of asymmetric edge reflection (the asymmetry in the reflections of the sample edges) to control the perfectly transmitting eigenchannel in a quasi-one-dimensional diffusive medium.

[Phys. Rev. B 92, 094203] Published Mon Sep 21, 2015

]]>The fractional quantum Hall effect is traditionally viewed as a distinctive attribute of strongly-interacting electron systems. This paper develops an alternative picture which suggests that the low energy quantum states corresponding to an experimentally observable filling fractions can be identified by simply having an exceptionally high degeneracy in the noninteracting limit.

[Phys. Rev. B 92, 125427] Published Mon Sep 21, 2015

]]>Using a variational ansatz based on matrix product states, the authors present a methodology for determine the elementary excitations and their low energy scattering matrices of general quasi-one-dimensional spin systems. From these scattering matrices, the authors map the system unto an effective integrable model and then employ the thermodynamic Bethe ansatz so as to determine thermodynamic properties of the spin system. As a demonstration of the method, the authors apply it to a Heisenberg spin ladder.

[Phys. Rev. B 92, 125136] Published Fri Sep 18, 2015

]]>Quantum spin liquids are elusive states of matter, which have been predicted more than four decades ago but have not so far been conclusively sighted in nature. In this paper the authors study the so called ‘extended Kitaev model’, which has a number of different quantum spin-liquid phases including one with non-Abelian excitations. They present a solution of a long standing problem for this model, namely, the problem of obtaining the dynamical response function. Using a rarely available exact calculation, they find that there are indeed clear signatures in the spin structure factor betraying the presence of spin-liquids and their fractionalized quasi-particles, including those with non-Abelian statistics.

[Phys. Rev. B 92, 115127] Published Mon Sep 14, 2015

]]>Entanglement in quantum many-body systems is one of the most challenging and fascinating recent trends in the study of complex quantum systems. A physical interpretation of the concept of “entanglement contour” is given using quantum many-body constructs and is generalized to the case of both fermionic and bosonic Hamiltonians within a unified framework. The relationship to number fluctuations and entropy is explored in a variety of free (quadratic) many-body systems.

[Phys. Rev. B 92, 115129] Published Mon Sep 14, 2015

]]>The coupling of the electric and magnetic degrees of freedom in condensed matter systems has long been an area of basic and applied research. In a 2013 PRL (PRL 110, 137205), a coupling energy term between the electromagnetic angular momentum density and the magnetization of a material was proposed. In this PRB, the authors provide a direct link between the proposed coupling term and the Dirac equation. They demonstrate that the Dirac equation leads to an interaction Hamiltonian (which they refer to as “angular magnetoelectric”, or AME, coupling Hamiltonian) that couples linearly the electron spin and the electromagnetic field’s angular momentum. They show that the AME coupling Hamiltonian has an expectation value that for some materials (e.g., ferromagnets) is equal to the recently proposed energy coupling, and that it contributes to the Inverse Faraday Effect. The AME coupling Hamiltonian may lead to the prediction and understanding of novel magnetoelectric and magneto-optical phenomena.

[Phys. Rev. B 92, 100402(R)] Published Fri Sep 11, 2015

]]>The spin susceptibility in strontium ruthenate is shown to undergo an increase when the material goes superconducting, a result in variance with most superconductors that we know. This behavior, once predicted for ${}^{3}$He too, is the surest sign that strontium ruthenate is a spin-triplet superconductor.

[Phys. Rev. B 92, 100502(R)] Published Fri Sep 11, 2015

]]>Two-dimensional Fourier transform (2DFT) spectroscopy is a cutting-edge technique to investigate nonlinear many-body physics in semiconductor nanostructures. This paper reports an experimental and theoretical study of 2DFT on a high-quality GaAs-based semiconductor microcavity to gain an understanding of polariton self-interactions and polariton cross-interactions and their effects on the 2D spectra.

[Phys. Rev. B 92, 125415] Published Fri Sep 11, 2015

]]>Ultrafast magnetization switching in ferrimagnets by an external laser pulse have been an active area of research in the last several years. Experimentally, the most intensively studied materials in which this phenomenon occurs are ferrimagnetic amorphous alloys, while the theoretical effort has been mostly concentrated on periodic crystalline structures. Understanding how and to what extent the inhomogeneity of the materials affects the magnetization switching is the focal point of this manuscript. By combining the first principles calculations with an atomistic model of the magnetization dynamics the authors construct a multi-scale theory that reproduces the experimentally observed magnetization dynamics in Gd-Fe alloys.

[Phys. Rev. B 92, 094411] Published Wed Sep 09, 2015

]]>This theoretical study provides an exact implementation of the CNOT two-qubit gate operation between capacitively coupled exchange-only qubits defined by three electrons in triple quantum dots. The authors show that the CNOT gate can be implemented by tuning three parameters: the two single-qubit exchange splittings, and the duration of the pulse.

[Phys. Rev. B 92, 125409] Published Wed Sep 09, 2015

]]>GaAs is the prototype material considered as a replacement for silicon in CMOS technology owing to its high electron mobility. However, the high density of interfacial defect states found at GaAs/oxide interfaces, which prevents the proper operation of GaAs-based devices through Fermi-level pinning, hinders the development of GaAs-based technology. In this thorough first-principles study of defects at the GaAs/Al${}_{2}$O${}_{3}$ interface, the authors deliver results that are very significant for the identification of the origins of Fermi-level pinning at these interfaces.

[Phys. Rev. B 92, 125304] Published Tue Sep 08, 2015

]]>Shear viscosity for a fermionic fluid described by a single band Hubbard model is computed using dynamical mean field theory and found to violate the quantum limit.

[Phys. Rev. B 92, 125103] Published Tue Sep 01, 2015

]]>A new computational method is introduced that allows interpolation of the electron-phonon matrix elements in the space of localized Wannier functions, extending a previous method for study of polar semiconductors. The amount of broadening of the bands in GaAs due to electron-phonon scattering is presented, showing good agreement with experimental results. The method is shown to perform better than an empirical pseudopotential.

[Phys. Rev. B 92, 054307] Published Mon Aug 31, 2015

]]>The authors study the competing ferromagnetic (FM) and antiferromagnetic (AFM) interactions in the quantum spin ice candidate Yb${}_{2}$Ti${}_{2}$O${}_{7}$ using various probes and techniques. They show that it produces a continuum of broad excitations, where the coexistence of different magnetic characteristics indicates the compound lies at the FM and AFM phase boundary for the material. This suggests that the competition of states produces an unconventional ground state through quantum fluctuations.

[Phys. Rev. B 92, 064425] Published Mon Aug 31, 2015

]]>A systematic study of both the harmonic response and spin torque ferromagnetic resonance demonstrates that the spin Hall torque efficiency in a Pt-ferromagnetic (FM) structure is strongly dependent on the interface properties and the choice of the ferromagnetic materials, a key point that has until now not been made in spin Hall studies.

[Phys. Rev. B 92, 064426] Published Mon Aug 31, 2015

]]>In${}_{2}$O${}_{3}$ and Ga${}_{2}$O${}_{3}$ are both transparent conducting oxides with advantageous properties, but differing crystal structures. Alloying the two together could permit the tuning of materials properties such as band gaps, but raises the question of what the stable crystal structure would be. Using state of the art first principles calculations, the authors predict alloy properties as a function of composition, finding the structure with the lowest formation barrier. They also report natural band alignments which can aid in the design of heterostructures.

[Phys. Rev. B 92, 085206] Published Mon Aug 31, 2015

]]>The authors study classical Heisenberg antiferromagnets with long-range interactions in two and three dimensions. These antiferromagnets can arise as effective models of diluted Coulomb spin liquids in the zero-temperature limit. The authors develop a phase diagram of these models as a function of the strength of the effective interaction strength.

[Phys. Rev. B 92, 085144] Published Tue Aug 25, 2015

]]>The authors study the stuffed metallic pyrochlore Pr${}_{2+x}$Ir${}_{2-x}$O${}_{7-\delta}$ through specific heat, elastic neutron scattering, and muon spin rotation ($\mu $SR) measurements. They consider the question of why the static local field (B${}_{l\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}c}$) as measured in $\mu $SR is so small. They weigh two possible theories, the fluctuating-moment picture and the suppressed-moment picture, and argue that the available evidence leans toward the former, while stating that regardless of picture, this pyrochlore is very close to a magnetic-nonmagnetic critical point.

[Phys. Rev. B 92, 054432] Published Mon Aug 24, 2015

]]>Using a novel hydrothermal ion-exchange technique, large and high-quality optimally doped single crystals of the new superconductor (Li${}_{0.84}$Fe${}_{0.16}$)OHFe${}_{0.98}$Se have been successfully synthesized for the first time. Thanks to these single-crystal samples, the anomalous normal-state properties of a linear in-plane electric resistivity, a dip in the Hall coefficient, and a linear magnetic susceptibility are revealed for the first time.

[Phys. Rev. B 92, 064515] Published Mon Aug 24, 2015

]]>Using bcc Fe as a playground, the authors investigate the presence of chiral degeneracies in realistic band structures of ferromagnetic materials. They find ubiquitous Weyl points and demonstrate that Chern numbers can be transferred between Fermi sheets by varying the Fermi level or an external parameter such as the magnetization direction.

[Phys. Rev. B 92, 085138] Published Fri Aug 21, 2015

]]>Heavy fermion systems are useful for studying quantum criticality because the low energy scale associated with their large effective mass can be tuned by nonthermal control parameters. Here, Shubnikov-de Haas oscillations are observed in YbPtBi, a heavy fermion compound with an exceptionally large effective mass for electrons, at a high magnetic field that reveals the shape of the Fermi surface. In the future these observations, when combined with additional data at lower magnetic fields, could provide important information about quantum criticality in these systems.

[Phys. Rev. B 92, 085135] Published Thu Aug 20, 2015

]]>To understand the pairing symmetry and superconducting transition temperature in heavily electron-doped iron-based superconductors, it is important to study more of these materials, especially ones with decent stability in air and without phase separation. Here, angle-resolved photoemission spectroscopy probes the surface electronic structure and superconducting gap in the new superconductor (Li${}_{0.8}$Fe${}_{0.2}$)OHFeSe, which shows a ${T}_{c}$ as high as 40 K.

[Phys. Rev. B 92, 060504(R)] Published Tue Aug 18, 2015

]]>Longitudinal magnetoresistance has recently been used as an experimental tool to identify exotic topological phases such as Weyl semimetals. The authors of this paper show that in the presence of certain scattering mechanisms generic materials can demonstrate similar characteristics as well, including negative longitudinal magnetoresistance.

[Phys. Rev. B 92, 075205] Published Mon Aug 17, 2015

]]>Muonium is like hydrogen, but with a positively charged muon instead of a proton at the center. Observing muon spin rotation in a single crystal of TiO${}_{2}$, and comparing to existing data for hydrogen, the authors demonstrate that the defect configuration and electronic structure are the same for both. This provides important support for research which uses muons as a substitute for hydrogen in semiconductors.

[Phys. Rev. B 92, 081202(R)] Published Mon Aug 17, 2015

]]>The authors in this work consider the orthogonality catastrophe in a new context, that of disordered quantum spin chains. Here the orthogonality catastrophe arises from measuring the overlap of the spin chain’s ground state before and after cutting the system into two. Unlike the orthogonality catastrophe in a metal, here the orthogonality catastrophe exhibits multifractality: different disorder-averaged moments of the overlap exhibit different scaling exponents with system size.

[Phys. Rev. B 92, 054203] Published Fri Aug 14, 2015

]]>The connection between the spin-orbit torque (SOT) and inverse spin-orbit torque (ISOT) in systems without inversion symmetry is studied by combining phenomenological models, diffusion theory, and density functional theory. Using this, DFT calculations on Co/Pt(111) magnetic bilayers expose the mechanisms underlying SOT and ISOT and highlight their reciprocity on the microscopic level.

[Phys. Rev. B 92, 064415] Published Wed Aug 12, 2015

]]>At low temperatures, the longitudinal resistivity of metallic systems exhibits quantum oscillations when submitted to a sufficiently high magnetic field. The authors report magneto-transport study of a high quality magnetic two-dimensional electron gas formed in a diluted magnetic CdMnTe quantum well. They find that the Shubnikov-de Haas characteristics is well-described by incorporating the electron Mn exchange interaction into the traditional Lifshitz-Kosevich formalism in a “mean field” approach.

[Phys. Rev. B 92, 085304] Published Wed Aug 12, 2015

]]>Motivated by the possibility of experimental detection of the topological magnetoelectric effect the authors put forth a theoretical proposal for its realization in the zero plateau quantum anomalous Hall state of a ferromagnet-topological insulator heterostructure.

[Phys. Rev. B 92, 081107(R)] Published Mon Aug 10, 2015

]]>Organic molecular magnets like piperazinium hexachlorodicuprate (PHCC) have attracted interest due to their sensitivity to pressure which presents possibilities for pressure-induced quantum phase transitions. Previous neutron and muon studies of PHCC gave differing indications of how the spin gap in this material varied with applied pressure. The authors of this work have resolved this discrepancy by further neutron scattering results showing that the spin gap has dissipated completely by 9 kbar, in agreement with the previous muon data. The authors also present a model in which the results are explained by the weakening of a single exchange pathway.

[Phys. Rev. B 92, 054413] Published Fri Aug 07, 2015

]]>The authors describe two theoretical setups that could be used to demonstrate the yet unobserved topological magnetoelectric effect. The first proposal employs the zero-filling quantum Hall effect in thin films under magnetic field. The second setup involves topological insulator thin films doped with two magnetic ions such as Cr and Mn.

[Phys. Rev. B 92, 085113] Published Fri Aug 07, 2015

]]>For several decades LaCoO${}_{3}$ attracted interest due the unconventional thermally-driven spin-state crossover from a nonmagnetic to paramagnetic state. More recently, it was realized that the “nonmagnetic” ground state harbors some form of magnetism that is likely due to local magnetic entities forming at oxygen vacancies. Such entities dubbed “magnetic excitons” were predicted in 1996, with some evidence for their existence emerging around 2005 from muon spin relaxation. In this Rapid Communication the authors provide the first scattering-based evidence for spin excitons, direct information on the size and density of the excitons, as well as their interactions. The form of the scattering is also direct proof of a bulk 3D ensemble of these excitons.

[Phys. Rev. B 92, 060404(R)] Published Thu Aug 06, 2015

]]>The shift of attention in topological matter is quickly shifting from topological insulators to Weyl semimetals after the recent much publicized theoretical prediction and experimental verification in TaAs. Reported here is the first Raman study of a Weyl semimetal. As with topological insulators, Raman phonons will be routinely used as probes to characterize the quality and the conditions of samples and devices. The study here identifies all the optic phonon modes and finds some additional interesting features, and should provide a good guide for future work.

[Phys. Rev. B 92, 064302] Published Thu Aug 06, 2015

]]>The authors study the diluted spin-half Heisenberg model near the percolation threshold using Schwinger boson mean field theory (SBMFT). They show how SBMFT predicts the emergence of effective local spin degrees of freedom. They demonstrate that SBMFT applied to dilute spin systems is qualitatively accurate by also performing DMRG computations.

[Phys. Rev. B 92, 064401] Published Mon Aug 03, 2015

]]>Defect two-level systems (TLS) ensembles are well known to be responsible for the low-frequency noise in solid-state mesoscopic devices, but are generally considered to be non-interacting. A model based on interactions between TLS, believed to reside in the surface oxide covering the superconducting material, provides a novel mechanism to explain the noise fluctuations that are present in virtually all superconducting circuit designs, the origins of which have remained elusive so far.

[Phys. Rev. B 92, 035442] Published Fri Jul 31, 2015

]]>EuTiO${}_{3}$ has been attracting considerable attention due to its large magnetoelectric effect and its potential for future applications. In this work the authors focus on the structural phase transition that bears resemblance to the prototypical phase transition in isostructural SrTiO${}_{3}$ but takes place at much higher temperatures ${T}_{S}$. The authors perform a detailed study of poly- and single-crystalline EuTiO${}_{3}$ and EuTi${}_{1-x}$Nb${}_{x}$O${}_{3}$ using synchrotron X-ray diffraction, Resonant Ultrasound Spectroscopy, and magnetization measurements. They find an unexpectedly rapid increase of ${T}_{S}$ when EuTiO${}_{3}$ is doped with niobium. Another notable result of the Nb doping, which is confirmed in this study for single-crystalline samples, is an unusual transformation of the low-temperature phase from an antiferromagnetic to ferromagnetic state at $x=0.1$.

[Phys. Rev. B 92, 024109] Published Thu Jul 30, 2015

]]>Quantum oscillations measurements on PdCrO${}_{2}$ show that the Fermi surface of the antiferromagnetically ordered state is a consequence of reconstruction of the Fermi surface of the unordered state.

[Phys. Rev. B 92, 014425] Published Wed Jul 29, 2015

]]>Motivated by the question of topological classification in interacting models the authors study an exactly solvable two-leg ladder model of spinless fermions with attractive interactions and find its ground states and correlation functions. They also demonstrate the appearance of topologically protected edge states and derive their braiding properties on a microscopic level.

[Phys. Rev. B 92, 041118(R)] Published Wed Jul 29, 2015

]]>Magnetic tunnel junctions (MTJs) are the building blocks of the magnetic random access memory technology due to their large contrast of the electrical resistances between the two different magnetic configurations. This work is focused on their configuration-dependent thermal properties. For the first time, the magneto-Peltier effect, a reciprocal effect of the magneto-Seebeck effect in magnetic tunnel junctions, is detected experimentally. These results open up the possibility of a magnetically controllable cooling mechanism in MTJs, which can be potentially applied in novel magnetic logic devices.

[Phys. Rev. B 92, 020414(R)] Published Tue Jul 28, 2015

]]>By exploiting epitaxial stabilization for materials synthesis in combination with $i\phantom{\rule{0}{0ex}}n$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ angle-resolved photoemission spectroscopy, the authors study the doping evolution of the archetypal infinite-layer cuprate Sr${}_{1-x}$La${}_{x}$CuO${}_{2}$ and uncover a surface reconstruction that is likely related to its polar structure.

[Phys. Rev. B 92, 035149] Published Tue Jul 28, 2015

]]>After the discovery of a 2D electron gas at the interface between LaAlO${}_{3}$ and SrTiO${}_{3}$, a great effort has been devoted to the investigation of possible routes to manipulate this system in order to exploit its interesting properties in practical applications. In this work the authors use a Landau model to show that a similar 2-dimensional electron gas may spontaneously form at ferroelectric interfaces. Unlike in the case of the LaAlO${}_{3}$/SrTiO${}_{3}$ interface, the properties of this system can be tuned in a nonvolatile way with the application of an electric field through its coupling with the ferroelectric polarization. This, for instance, would allow to induce a metal/insulator transition or to switch between an electron and a hole gas using an electric field. Such properties open new avenues for the use of 2D electron gases in oxide interfaces.

[Phys. Rev. B 92, 035438] Published Tue Jul 28, 2015

]]>Convincing experimental data show that CaMn${}_{2}$Al${}_{10}$ presents itinerant Mn-magnetism on the cusp of ferromagnetic order, opening up a new material to explore the relationship between quantum criticality and possible exotic ground states.

[Phys. Rev. B 92, 020413(R)] Published Fri Jul 24, 2015

]]>Two- and three-dimensional semi-metallic systems have recently emerged as an exciting arena in which to explore the effects of interactions in itinerant electron systems, and to advance the understanding of competing orders in strongly correlated materials. In this work, a study of the critical behavior of a three-dimensional parabolic semimetal in proximity to a quantum phase transition into a ferromagnetic phase demonstrates that the quantum critical point is unstable toward the formation of an incommensurate spin density wave phase.

[Phys. Rev. B 92, 035137] Published Tue Jul 21, 2015

]]>Inspired by helicity dependent optical phenomena in chiral metamaterials the authors exploit the idea of helicity degree of freedom of Dirac fermions. They perform a first-principles study of SnTe films and show that giant helicity splitting in the band structures can be induced under moderate electric field. They suggest using helicity as an extra degree of freedom for helicity-resolved filtering and focusing of Dirac fermions.

[Phys. Rev. B 92, 041408(R)] Published Tue Jul 21, 2015

]]>High-performance refractory materials play an important role in applications ranging from gas turbines to heat shields for hypersonic vehicles. The authors carried out an extensive first-principles investigation into the melting temperatures of the refractory Hf-C and Hf-Ta-C systems, which hold the highest melting temperatures known to date, and identified the major factors that contribute to the high melting temperatures. A new class of materials were proposed and explored, which, according to the calculation, may increase the current melting point record by up to 200 K. This work demonstrates the feasibility and usefulness of large-scale first-principles calculations for high-throughput materials screening on a high-level thermodynamic property.

[Phys. Rev. B 92, 020104(R)] Published Mon Jul 20, 2015

]]>Exploration of novel phenomena in oxides with strong spin-orbit coupling is one of the hot topics in condensed matter physics. The authors theoretically study the macroscopic magnetic anisotropy induced by fluctuations. By considering a spin model on fcc lattice with direction-dependent interactions, which may serve as an effective model for insulating magnetic oxides with strong spin-orbit coupling, they discover of a novel behavior in spin models with direction-dependent interaction.

[Phys. Rev. B 92, 020411(R)] Published Mon Jul 20, 2015

]]>The authors report structural, transport, magnetic and thermodynamic properties of of single-crystalline samples of Rb${}_{2}$Cr${}_{3}$As${}_{3}$ in both the normal and superconducting states. By compare them with those of K${}_{2}$Cr${}_{3}$As${}_{3}$ they argue for the evidence of reduced dimensionality and the ability to control it by structural tuning.

[Phys. Rev. B 92, 020508(R)] Published Mon Jul 20, 2015

]]>Although a century has passed since the celebrated Einstein - de Haas experiments, the microscopic mechanisms leading to the conversion of the spin angular momentum to the mechanical angular momentum in elastic solids has not been fully understood. In this paper D. A. Garanin and E. M. Chudnovsky explore the concept of the phonon spin recently suggested by L. Zhang and Q. Niu, Physical Review Letters 112, 085503 (2014). They show how it enters the problem of the relaxation of the atomic spin in the elastic body and explicitly demonstrate the conservation of the total angular momentum in spin-phonon processes at the microscopic level.

[Phys. Rev. B 92, 024421] Published Mon Jul 20, 2015

]]>Measurements of thermal and electrical transport at low temperature near an unconventional quantum critical point in $\beta $-YbAlB${}_{4}$ reveal that the Wiedemann-Franz law continues to be obeyed and Landau quasiparticles remain intact.

[Phys. Rev. B 92, 041114(R)] Published Mon Jul 20, 2015

]]>The authors report observation of extremely large magnetoresistance in two compounds which were recently suggested as candidates for Weyl semimetals.

[Phys. Rev. B 92, 041203(R)] Published Mon Jul 20, 2015

]]>The traditional methods for manipulating the magnetization precession resonantly by microwaves fail to operate at the nanoscale. In the present paper, by using a specially designed ferromagnetic structure, the authors demonstrate resonant driving of the magnetization precession at microwave frequencies by exploiting coherent lattice vibrations. They use a 59-nm ferromagnetic layer as cavity of a phononic Fabry-Perot nanoresonator formed by a semiconductor superlattice. The coherent phonons with resonance frequencies up to 30 GHz are excited by femtosecond laser pulses and feed the magnetization precession within their nanosecond lifetime. The amplitude of the precession increases drastically for resonant conditions when the frequency of the free precession is equal to the frequency of the driving magnetostrictive force.

[Phys. Rev. B 92, 020404(R)] Published Thu Jul 16, 2015

]]>The critical behavior of quantum Hall transitions in two-dimensional disordered electronic systems can be described by a class of non-unitary conformal field theories with logarithmic correlations. Using the replica trick and the underlying symmetries of these quantum critical points, the author shows how to construct non-perturbatively disorder-averaged observables in terms of Green’s functions that scale logarithmically at criticality.

[Phys. Rev. B 92, 014205] Published Wed Jul 15, 2015

]]>The new family of layered organic-inorganic perovskite crystals (OIPCs) is a unique addition to the set of available 2D materials. It is a crystalline inorganic solid that is surrounded by well-ordered organic ligands, both of which can be modified separately. This hybrid character endows the material with an unusual degree of tunability and flexibility. Here, the authors present their results on the synthesis and extensive characterization of 2D OIPC single-crystalline bilayers of (C${}_{4}$H${}_{9}$NH${}_{3}$)${}_{2}$PbI${}_{4}$. These materials could significantly expand the range of van der Waals heterostructures that can be produced by their combination with, e.g., graphene, $h$-BN layers, transition metal dichalcogenide layers, etc.

[Phys. Rev. B 92, 045414] Published Tue Jul 14, 2015

]]>Renormalization group analysis of the effects of disorder and interactions in two-dimensions shows that in some parameter regimes superconductivity can even be enhanced by localization effects.

[Phys. Rev. B 92, 014506] Published Mon Jul 13, 2015

]]>Nontrivial (hidden) symmetries present within extended Kitaev-Heisenberg model, have been recently introduced to capture the magnetism of layered honeycomb iridates Na${}_{2}$IrO${}_{3}$ and Li${}_{2}$IrO${}_{3}$. The authors study the hidden symmetries of a generic four-parameter nearest-neighbor spin model of iridates of the ${A}_{2}$IrO${}_{3}$ kind in the honeycomb lattice compounds under trigonal compression. Their method utilizes a mapping of the Hamiltonian on itself by using the symmetry of the Hamiltonian, which connects different points in its parameter space. They claim that a complete set of points of hidden SU(2) symmetry at which seemingly highly anisotropic model can be mapped back on the Heisenberg model and inherits therefore its properties such as the presence of gapless Goldstone modes.

[Phys. Rev. B 92, 024413] Published Mon Jul 13, 2015

]]>The interplay between superconductivity and magnetism is a complex but very interesting and technologically important topic in solid state physics. The rich physics resulting from the competition of these two phases has been studied so far with models and phenomenological approaches that leave the prediction of material-specific properties, such as the critical temperature ${T}_{c}$, or the magnetization, out of reach. Density functional approaches have been very successful in the prediction of the material specific magnetization via Spin-DFT on the one, and Tc for superconducting system via SCDFT on the other hand. In this work the authors present a fully $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ theory to describe the microscopic competition of magnetism and superconductivity, in the framework of a density functional theory unifying SpinDFT and SCDFT.

[Phys. Rev. B 92, 024505] Published Wed Jul 08, 2015

]]>This work presents the numerical solution of the equations derived in the companion manuscript “$A\phantom{\rule{0}{0ex}}b$ $I\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ Theory of Superconductivity in a Magnetic Field. I. Spin Density Functional Theory For Superconductors and Eliashberg Equations.” and the comparison of the methods presented therein. To perform this comparison the authors analyze a superconducting test system where free electron states couple via a phonon field and are Zeeman split by a tunable homogeneous magnetic field. It turns out that while the superconducting analogue of the Kohn-Sham (KS) density functional framework can accurately predict the superconducting critical temperature, it also suffers from the analogue of the “band gap” problem for the quasiparticle spectrum in the superconducting state. The authors resolve this problem by introducing a generalization of the ${G}_{0}$${W}_{0}$ approximation to superconductors.

[Phys. Rev. B 92, 024506] Published Wed Jul 08, 2015

]]>Motivated by the question of whether or not two gapped Hamiltonians belong to the same phase, the authors compare two exactly solvable lattice models. They show that the only way to see that these models belong to distinct phases is to examine their three-loop braiding statistics.

[Phys. Rev. B 92, 035115] Published Wed Jul 08, 2015

]]>Angle-resolved photoemission shows the existence of two-dimensional metallic states of confined itinerant electrons at the (001) and (101) surfaces of insulating TiO${}_{2}$ anatase. This is a material of much current interest, as a photocatalyst or a transparent conducting oxide, for instance. The 2D electron gases come from the formation of oxygen vacancies in the near-surface region, created by exposure to ultraviolet irradiation. The results here open a route to nano-engineering these confined electronic states using ultraviolet light, controlling their metallic or insulating nature.

[Phys. Rev. B 92, 041106(R)] Published Wed Jul 08, 2015

]]>It was reported earlier that alkali metal doped picene shows superconductivity at rather high temperatures. In this paper the authors have prepared such materials and thoroughly analyzed them using a variety of measurements. They conclude that superconductivity in doped hydrocarbons is questionable, casting doubts on the previous interpretation of the data.

[Phys. Rev. B 92, 014502] Published Tue Jul 07, 2015

]]>Sr${}_{3}$Ir${}_{2}$O${}_{7}$ is a member of the iridate Ruddlesden-Popper series Sr${}_{n+1}$Ir${}_{n}$O${}_{3n+1}$ with electronic properties that interpolate between the insulating single-layer Sr${}_{2}$IrO${}_{4}$ ($n=1$) and a metallic compound SrIrO${}_{3}$ ($n=\mathrm{\infty}$). Using resonant inelastic X-ray scattering (RIXS) experiments, the authors reveal a new magnetic mode and propose a model based on weakly coupled quantum dimers to describe the observed excitation spectrum.

[Phys. Rev. B 92, 024405] Published Mon Jul 06, 2015

]]>The authors study magneto-electric properties of several hexagonal manganites and ferrites (HoMnO${}_{3}$, ErMnO${}_{3}$, YbMnO${}_{3}$, LuMnO${}_{3}$, and LuFeO${}_{3}$). By disentangling the contributions of exchange striction and the spin-orbit coupling, they propose HoMnO${}_{3}$ as a promising candidate material with magneto-electric coefficient reaching 15 ps/m.

[Phys. Rev. B 92, 035107] Published Mon Jul 06, 2015

]]>The authors study a generic quantum dot close to the particle-hole symmetric point. By first mapping the model onto an equivalent two-level system coupled to spin-polarized leads, they are able to study the system as a function of magnetic field at large bias voltage. Doing so they are able to identify a non-equilibrium fixed point of the model.

[Phys. Rev. B 92, 041103(R)] Published Mon Jul 06, 2015

]]>The tungsten ditelluride WTe${}_{2}$ semimetal is known for if its extremely large magnetoresistance. The authors measure the angular dependence of this magnetoresistance and find that when the magnetic field is applied parallel to the tungsten chains (along the $a$ axis), the very large magnetoresistance (as high as 1200% at 15 T and 2 K) no longer exhibits a conventional quadratic but rather a linear field dependence.

[Phys. Rev. B 92, 041104(R)] Published Mon Jul 06, 2015

]]>The study of Raman scattering processes in the ultraviolet excitation energy range is not common in carbon-based materials. This paper reports that the widely known double-resonant Raman scattering, which is dominant in the visible excitation energy in these materials, is suppressed in the UV range. This is an important development because one can now measure two-phonon densities of states that were not accessible before. The results demonstrate the high potential of UV Raman spectroscopy for research on graphitic nanocarbons.

[Phys. Rev. B 92, 041401(R)] Published Wed Jul 01, 2015

]]>While efficient algorithms exist for the simulation of bosons simulations of fermions are more challenging because of the infamous fermion sign problem. In this paper the authors take a step toward solution and develop continuous-time quantum Monte Carlo algorithm for lattice fermions that scales linearly with projection time and interaction strength. This method is benchmarked on the problem of the fermionic quantum critical point of spinless fermions on a honeycomb lattice.

[Phys. Rev. B 91, 235151] Published Tue Jun 30, 2015

]]>Much attention has been devoted recently to identify possible ways to overcome the notorious sign problem encountered in quantum Monte Carlo simulations. The authors of this paper propose a new method based on Majorana representation of complex fermions, which they dub Majorana Quantum Monte Carlo (MQMC). They find a class of SU(N) fermionic models which are sign-free in MQMC but cannot be solved with other available methods.

[Phys. Rev. B 91, 241117(R)] Published Tue Jun 30, 2015

]]>Nonsymmorphic materials, which possess special symmetry operations (screw rotation, glide mirror), have been theoretically reexamined in recent years for possible novel quantum phases or electronic functions derived from the symmetry requirements. Here, the authors demonstrate that in the typical nonsymmorphic material IrO${}_{2}$, the type of charge carrier (electron or hole) is strongly dependent on the crystal orientation and capable of being switched by a magnetic field. This remarkable effect is seen in electrical transport measurements on various thin films supported by simple tight-binding and band structure calculations.

[Phys. Rev. B 91, 241119(R)] Published Tue Jun 30, 2015

]]>Dislocations are central to the understanding of plasticity in metals. Using density functional theory the authors show that interstitial carbon atoms in ferritic steels stabilize a dislocation core configuration called a hard core which is otherwise unstable. Since, as they also show, at equilibrium all dislocations are expected to be fully decorated by carbon atoms, this has important implications for the understanding of plasticity in ferritic steels. It is expected that the picture developed here could also be applicable to other solutes besides carbon and to other metals besides iron.

[Phys. Rev. B 91, 220102(R)] Published Mon Jun 29, 2015

]]>Infrared spectroscopy of VO${}_{2}$ thin films at high spatial resolution shows new electronic and lattice states due to epitaxial strain that differ fundamentally from those in the bulk. This is the first ultra-broadband infrared near-field study of a correlated electron material, made possible by the newly developed synchrotron infrared near-field spectroscopy method (SINS) on the Advanced Light Source at Lawrence Berkeley National Laboratory.

[Phys. Rev. B 91, 245155] Published Mon Jun 29, 2015

]]>The authors study the proton correlations present in water ice in its ice rule phase ${I}_{h}$. Using an effective field theory, an analytic form for the correlation function is derived and then compared against numerics, showing excellent agreement. This field theory is argued to be a U(1) gauge theory in its deconfined Coulomb phase.

[Phys. Rev. B 91, 245152] Published Thu Jun 25, 2015

]]>The formation of extended electron states in one-dimensional nanostructures is of key importance for the function of molecular electronics devices. In this paper, using a combination of atomic force microscopy, scanning tunneling spectroscopy, and tight-binding calculations the authors investigate the confinement of electronic states to controlled Cl vacancy pairs in a NaCl bilayer on Cu(111). They reveal that electron-phonon coupling has great influence on these quantities.

[Phys. Rev. B 91, 235443] Published Wed Jun 24, 2015

]]>Can the two-dimensional interaction driven Mott metal-insulator transition be continuous? Motivated by experiments on quasi two-dimensional organics that may show such a transition the authors study a two-leg triangular Hubbard strip. They argue that this model harbors a continuous Kosterlitz-Thouless-like quantum phase transition between a metal and a gapless spin liquid.

[Phys. Rev. B 91, 235140] Published Tue Jun 23, 2015

]]>A theoretical formalism is developed to calculate the optical force induced within a 2D metamaterial, based on the electrostrictive tensor. It turns out that it is not always straightforward to use the usual effective-medium parameters $\u03f5$ and $\mu $ of the metamaterial for obtaining the body force density. The findings are tested via a 2D array of parallel infinitely long dielectric cylinders and the analytical theory is in excellent agreement with numerics. The correct stress tensor to describe the force density in an effective medium is the Helmholtz one rather than the Maxwell. The theory, though, is not exact and points to a fundamental limitation of effective medium theory in describing light-induced body forces.

[Phys. Rev. B 91, 235439] Published Tue Jun 23, 2015

]]>Polar zinc titanate (ZnTiO${}_{3}$) is a promising lead-free ferroelectric compound with high spontaneous polarization of 75 $\mu \phantom{\rule{0}{0ex}}C/c\phantom{\rule{0}{0ex}}{m}^{2}$, which is comparable with that of PbTiO${}_{3}$. In this work a collaboration of researchers from Germany, UK, and USA present a detailed investigation of vibrational properties of ZnTiO${}_{3}$ via the high-pressure Raman spectroscopy, second-harmonic generation, and $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations.

[Phys. Rev. B 91, 214110] Published Mon Jun 22, 2015

]]>Thorough experimental investigations from this group provide new data and cogent understanding of the effects of copper substitution in iron telluride over a broad substitution range. They also show how subtle changes in copper substitution and an applied magnetic field modify the low-temperature magnetic and structural phases in these materials, as well as the nature of the transitions into these phases.

[Phys. Rev. B 91, 224424] Published Mon Jun 22, 2015

]]>Using broadband spectroscopic ellipsometry, the authors determine the complex valued dielectric function of silver films from 0.05 eV (λ=25 μ) to 4.14 eV (λ = 300 nm) with a statistical uncertainty of less than 1%. While several previous similar measurements exist, they span considerably shorter energy ranges and report partially inconsistent results. In view of the wide-ranging applications of silver in nanophotonics, plasmonics and optical metamaterials, we anticipate this paper to become a standard reference for many scientists and engineers.

[Phys. Rev. B 91, 235137] Published Mon Jun 22, 2015

]]>This works brings us a step closer towards the realization of the quantum spin Hall (QSH) effect. Using electronic structure calculations, the authors suggest that a family of the single-layer 2D transition metal dichalcogenide haeckelites $M\phantom{\rule{0}{0ex}}{X}_{2}$ ($M$=W or Mo, $X$=S, Se, or Te) can host the QSH effect at high temperatures. Their work also implies that a square-lattice 2D material can host a nontrivial topological state, thus, extending the search boundaries for topological materials beyond the ones with a hexagonal lattice.

[Phys. Rev. B 91, 235434] Published Fri Jun 19, 2015

]]>Experimental measurement of topological degeneracy of fractional quantum Hall states is obstructed by the requirement of a torus geometry. The authors propose an alternative scheme which relies on the realization of ground state degeneracy in an effective torus geometry. It is achieved by gluing the edges of a bilayer annulus, where the layers are occupied by electron and hole fractional quantum Hall states or by a topological insulator.

[Phys. Rev. B 91, 245144] Published Fri Jun 19, 2015

]]>In quantum mechanics, weak measurement allows one to measure off diagonal matrix elements of operators. In this work, the author designs a weak value protocol which can be harnessed to measure the topological invariant of a quantum spin Hall insulator.

[Phys. Rev. B 91, 241109(R)] Published Thu Jun 18, 2015

]]>Recently D. I. Khomskii proposed that the elementary excitations in spin ice materials, the magnetic monopoles, also possess electric dipole moments. In this manuscript the properties of such magneto-electric monopoles are explored within a model of spin ice materials that includes nearest-neighbour coupling, Zeeman energy, electric and magnetic dipolar interactions, with a particular emphasis on a prototype spin-liquid pyrochlore Tb${}_{2}$Ti${}_{2}$O${}_{7}$.

[Phys. Rev. B 91, 214422] Published Wed Jun 17, 2015

]]>A single unit cell FeTe${}_{1-x}$Se${}_{x}$ film consisting of a flat square Fe layer sandwiched between two Se/Te monolayers shows a fully gapped tunneling spectrum with superconducting gaps up to ~16.5 meV, nearly ten times the gap value of an optimally doped bulk single crystal. Compared with the ${T}_{c}$~14.5 K of bulk FeTe${}_{0.6}$Se${}_{0.4}$, a gap of ~16.5 meV could correspond to a transition temperature higher than the boiling temperature of liquid-nitrogen (77 K). Initial $e\phantom{\rule{0}{0ex}}x$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ transport measurements reveal an onset superconducting transition temperature above 40 K, nearly two times higher than that of the optimally doped bulk single crystal FeTe${}_{0.6}$Se${}_{0.4}$.

[Phys. Rev. B 91, 220503(R)] Published Wed Jun 17, 2015

]]>Fe atoms adsorbed on Cu(111) have been used as an atomic-scale model system for performing spin-based logic operations and to build the smallest stable magnet. In pursuit of understanding the strength of the adatom/substrate hybridization in this system, small Fe clusters down to single atoms adsorbed on a Cu(111) surface were studied using X-ray Absorption Spectroscopy and X-ray Magnetic Circular Dichroism experiments. The spin and orbital moments as well as the magnetic anisotropy energies were extracted experimentally and compared with density functional theory and multiplet calculations. The results show an unexpectedly sharp atomic-like multiplet feature for single Fe atoms which disappears with increasing coverage and cluster size. This indicates a surprisingly weak hybridization of the Fe 3d states to the electronic states of the Cu(111) substrate.

[Phys. Rev. B 91, 235426] Published Tue Jun 16, 2015

]]>In this paper the authors study the dependence of the visibility of the Aharonov-Bohm oscillations of an electronic Mach-Zehnder interferometer upon the transmission properties of an additional quantum point contact placed in front of the interferometer’s input. According to a theory by I. P. Levkivskyi and E. V. Sukhorukov ( Phys. Rev. Lett. 103, 036801 (2009)), a non-equilibrium noise-induced phase transition is meant to occur when the transmission of the point contact equals 1/2. The authors present experimental evidence for the existence of this critical point.

[Phys. Rev. B 91, 245419] Published Tue Jun 16, 2015

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