On the basis of novel insight in the physics of Majorana modes, the authors solve the microscopic mechanism of the anomalous proximity effect and propose an experimental setup for its observation.

[Phys. Rev. B 91, 174511] Published Fri May 15, 2015

]]>The overheating of microprocessors components is currently the most limiting factor in the development of information technology. This motivates the concern in finding innovative ways to control and evacuate heat in nanoscale devices. In the presence of a magnetic field B, the heat currents flowing through a generic setup exhibit reversible and irreversible components: the former are reversed when inverting B→-B, whereas the latter remain unchanged. In this work the authors exploit this feature to propose a magnetic thermal switch: a setup which allows control of the heat flow by making use of an external magnetic field as a selector of a desired working configuration. Several features, like switching on/off, inversion, partition and swap of the heat currents, can be implemented in a programmable device allowing full controllability. Among the advantages of this approach are the absence of any temperature constraints and the possibility to control phononic, in addition to electronic, heat flows.

[Phys. Rev. B 91, 205420] Published Thu May 14, 2015

]]>Mesoscopic circuits can be coupled to microwave cavities to form hybrid light-matter systems. This emerging field represents an intermediate regime between standard cavity and circuit quantum electrodynamics. In this paper, the authors develop a general method based on a photonic pseudo-potential to describe the electric coupling between electrons in a nanocircuit and cavity photons.

[Phys. Rev. B 91, 205417] Published Wed May 13, 2015

]]>Topological phases of matter lack conventional local order parameter but might have hidden orders. This is exemplified by quantum Hall states for which Laughlin’s wavefunction approach revealed a connection between topological phases and broken symmetry. The authors utilize this approach to construct candidate wave functions for one- and two-dimensional symmetry-protected phases (SPT) and provide evidence that their candidate states do in fact belong to SPT.

[Phys. Rev. B 91, 195117] Published Tue May 12, 2015

]]>This is a comprehensive Raman scattering study of electrochemically gated graphene transistors. A robust, highly accurate determination of the Fermi level, electron-phonon coupling, and defect scattering rates is achieved. Fermi energies as high as 700 meV above the Dirac point were achieved in ambient conditions, without damaging graphene. This opens exciting perspectives for optoelectronics.

[Phys. Rev. B 91, 205413] Published Tue May 12, 2015

]]>Authors observe a new magnetoresistance phenomenon in a relativistic structure which allows them to detect a 180 degrees magnetization reversal without breaking the symmetry between the two states by a magnetic field or a reference ferromagnet.

[Phys. Rev. B 91, 180402(R)] Published Mon May 11, 2015

]]>Theoretical predictions and experimental results demonstrate that mu-near zero metamaterials allow enhanced transmission (supercoupling) between two waveguides coupled by a channel with a disproportionately wide cross section. This effect is related but distinctly different from (and cannot be reduced to) a previously reported supercoupling effect using epsilon-near-zero metamaterials.

[Phys. Rev. B 91, 195112] Published Mon May 11, 2015

]]>Requirement of adiabaticity in the process of braiding of Majorana modes presents serious challenges to its practical implementation. The authors explore how to minimize nonadiabatic errors for finite braiding times by finding an optimal protocol for the Majorana movement. They show, counterintuitively, that protocols characterized by sharp transitions between Majorana motion at maximal and minimal velocities may do the trick.

[Phys. Rev. B 91, 201404(R)] Published Mon May 11, 2015

]]>Motivated by the appearance of optically induced superconductivity in the stripe-ordered La${}_{1.885}$Ba${}_{0.115}$CuO${}_{4}$ cuprate, this group uses time-resolved THz spectroscopy to map out the enhancement of interlayer superconducting coupling as a function of both temperature and time delay, for different pump wavelengths and fluences.

[Phys. Rev. B 91, 174502] Published Tue May 05, 2015

]]>Electrochemical doping in 2D transition-metal dichalcogenides (TDMs) aimed at creating field effect transistor (FET) conditions can allow one to explore interesting transport phenomena in reduced dimensionality. In this timely work, the authors thoroughly investigate from first principles how field-effect doping affects the structural properties, electronic structure, and Hall coefficient of mono- and few-layers TDMs. They show that (i) the models, typically, used to estimate the doping charge in FET devices cannot be applied to 2D TMDs and, (ii) given the multivalley nature of both the conduction and valence bands, small differences in the band structure can manifest in transport behavior that is very different from that predicted based on a single parabolic band.

[Phys. Rev. B 91, 155436] Published Thu Apr 30, 2015

]]>Can topologically non-trivial states, such as those in topological insulators and superconductors, arise in the mixed states of open quantum systems? By imposing special constraints on the gauge structure of the density matrices which describe open quantum systems, the authors find non-trivial topological invariants showing that topological phenomena can be generalized to mixed states. The method is illustrated with an analysis of Chern insulators at finite temperature.

[Phys. Rev. B 91, 165140] Published Thu Apr 30, 2015

]]>The paper reports the observation of an anisotropic capacitance in a parallel plate $p$-$n$ junction capacitor where one plate is a ferromagnetic semiconductor, GaMnAs, and the other is nonmagnetic $n$-doped GaAs. The capacitance depends on the angle of the magnetization of the ferromagnetic plate and is analogous to the tunneling anisotropic magnetoresistance, which originates from the spin-orbit interaction. This can be an important effect in magnetic sensor applications.

[Phys. Rev. B 91, 140409(R)] Published Wed Apr 29, 2015

]]>This paper reports on the experimental and theoretical investigation of nonequilibrium Kondo effect in carbon nanotube quantum dots. At low temperature and in the absence of magnetic field, the authors observe two symmetric satellite features on either side of the zero bias peak due to the splitting of single-particle states by the spin-orbit coupling and valley mixing. Further experimental results are discussed based on the underlying symmetries of the carbon nanotube energy spectrum.

[Phys. Rev. B 91, 155435] Published Wed Apr 29, 2015

]]>The authors consider the phenomena of quantum revivals in a system exhibiting many-body localization. To this end the authors study a qubit attached to a disordered insulator. Without interactions, the qubit undergoes revivals at a rate that approaches a constant as time goes to infinity. If interactions are added to the insulator, this rate sees instead a logarithmic suppression in time. This logarithmic behavior is related to the same mechanism that underpins the logarithmic growth in entanglement entropy after a quantum quench in a many-body localized system.

[Phys. Rev. B 91, 140202(R)] Published Mon Apr 27, 2015

]]>Inelastic scattering of electrons on crystals can excite lattice vibrations known as phonons. An energy resolution of 10 meV in the scattered electron energy loss has recently been demonstrated in scanning transmission electron microscopy (STEM), permitting experimenters to distinguish between elastic and inelastic scattering events. In this paper the authors present simulations showing that, with the recent improvement in energy resolution, atomic resolution phonon spectroscopy and imaging of crystals using STEM should now be feasible.

[Phys. Rev. B 91, 144108] Published Mon Apr 20, 2015

]]>Cu${}_{x}$Bi${}_{2}$Se${}_{3}$ is a material of significant recent interest and controversy, as it might be a topological superconductor. However, it is now apparent that different preparation routes yield crystals with different properties. This group offers the first systematic study of the preparation-dependence of superconductivity in this material.

[Phys. Rev. B 91, 144506] Published Mon Apr 20, 2015

]]>The topological central charge is a property that takes the same value throughout a topological phase of matter. In this work authors show how to compute topological central charge as a Berry curvature associated with position-dependent changes in the spatial metric in the bulk of the system.

[Phys. Rev. B 91, 165306] Published Mon Apr 20, 2015

]]>According to a recent theoretical conjecture for a classification of symmetry protected topological (SPT) phases which can arise in a collection of lattice boson models called group cohomology models, each model belongs to a distinct SPT phase, and each SPT phase can be realized by a model. Here the authors show that for SPT phases with symmetry groups that are finite, Abelian, and unitary, each group cohomology model can be characterized by a unique set of topological invariants and therefore belongs to a distinct SPT phase. In two dimensions it is further shown that the complete set of group cohomology models accounts for all SPT phases, while in three dimensions evidence pointing toward such a proof is found.

[Phys. Rev. B 91, 165119] Published Wed Apr 15, 2015

]]>Near-field electromagnetic heat transfer is studied in a theoretical semiconductor heterojunction system in the presence of a non-zero chemical potential (via a bias voltage). Changing the potential enables electronic control of near-field heat transfer and suggests a novel and very exciting new possibility for achieving solid-state cooling, a holy grail in thermal science.

[Phys. Rev. B 91, 134301] Published Mon Apr 13, 2015

]]>Synthesis of a new material in the iridate family with a continuously tunable valence of Ir shows the dominant role played by spin-orbit coupling in determining the magnetic properties.

[Phys. Rev. B 91, 155117] Published Mon Apr 13, 2015

]]>The much debated topology of Bi${}_{1-x}$Sb${}_{x}$ has been resolved in this very careful and thorough experiment. The authors optimized the Bi${}_{1-x}$Sb${}_{x}$ growth method and minimized surface imperfections. They performed direct measurements of the surface band structure and followed its evolution within a large window of Sb concentration. They did not detect a third surface band seen in previous experiments. Thus, they conclude that the experimental surface band structure of B${}_{1-x}$Sb${}_{x}$ in the topologically insulating regime now agrees well with the theoretical predictions.

[Phys. Rev. B 91, 161406(R)] Published Mon Apr 13, 2015

]]>Using high resolution THz spectroscopy, the authors study spinon confinement in the weakly coupled antiferromagnetic chain compound SrCo${}_{2}$V${}_{2}$O${}_{8}$. The confined spinons appear in a hierarchy that can be fully described by a one dimensional Schrödinger equation with a linear confinement potential.

[Phys. Rev. B 91, 140404(R)] Published Thu Apr 09, 2015

]]>In addition to its extraordinary mechanical, thermal and electrical properties, graphene shows great potential in manipulating electromagnetic fields. One of the main advantages of graphene compared to other materials is the extraordinary tunability of its conductivity, which can be achieved electrically by means of a back gate, or optically through the excitation of photocarriers. Scientists from Belgium, Sweden and the United States demonstrate that this tunability of graphene can be used in a novel setup for the generation of frequency combs. Traditionally, frequency combs are generated using nonlinear materials. The researchers studied the interaction between light and time-dependent graphene sheets, including both dispersion and explicit time-dependence of the conductivity. Based on this model, they demonstrated that frequency combs can be generated without material nonlinearities. Indeed, at terahertz frequencies it is possible to modulate the linear, time-dependent conductivity of graphene to obtain a large variety of frequency combs.

[Phys. Rev. B 91, 161403(R)] Published Wed Apr 08, 2015

]]>Motivated by recent measurements of state-selective intersystem crossing (ISC) in the nitrogen-vacancy (NV) center in diamond (see companion PRL), a new microscopic model is developed of the key ISC mechanism. These nonradiative transitions between states of different spin multiplicity are pivotal in the optical initialization and readout of the NV center’s electronic spin, which has created a diverse range of room-temperature applications in metrology and quantum information science.

[Phys. Rev. B 91, 165201] Published Wed Apr 08, 2015

]]>Improvements in experimental resolution allow this group to elucidate how the electronic nematic transition evolves in FeSe. They observe the changing Fermi surface, the position of the lowest energy electronic excitations, as well as the propensity towards nematic order and its manifestation under strain.

[Phys. Rev. B 91, 155106] Published Tue Apr 07, 2015

]]>Using semiclassical nonlinear sigma model techniques the authors classify a broad class of bosonic symmetry protected topological phases. This construction works in all dimensions.

[Phys. Rev. B 91, 134404] Published Mon Apr 06, 2015

]]>Diluted magnetic semiconductors have attracted much attention as candidates for spintronic devices after the discovery of ferromagnetism in Mn-doped GaAs. However, the limited chemical solubility of the magnetic element Mn together with the inability to control carrier density independently of the magnetic element concentration are major obstacles to material design and applications. The newly found diluted magnetic semiconductor Ba${}_{1-y}$K${}_{y}$(Zn${}_{1-x}$Mn${}_{x}$)${}_{2}$As${}_{2}$, which has the same crystal structure as the iron-based superconductor BaFe${}_{2}$As${}_{2}$, circumvents these problems and exhibits ferromagnetic transition temperatures as high as 230 K. Using x-ray absorption and resonance photoemission spectroscopy this group explicitly demonstrates that the ThCr${}_{2}$Si${}_{2}$-type crystal structure is an ideal framework both for high-temperature superconductivity and for ferromagnetism, and that the carrier-induced ferromagnetism of GaMnAs is operating in other ferromagnetic semiconductors.

[Phys. Rev. B 91, 140401(R)] Published Mon Apr 06, 2015

]]>First-principles calculations presented in this Rapid Communication suggest that a number of $A\phantom{\rule{0}{0ex}}B$ binary honeycomb monolayers should be ferroelectric. Dipoles arise from the buckled structure, and the polarization reversal occurs via switching the structural buckling which can be triggered by an external electric field. The authors address the emerging valley-dependent properties arising from the ferroelectric bistability and explore the intimate link between ferroelectricity, spin-valley physics, and Rashba spin-splitting phenomena.

[Phys. Rev. B 91, 161401(R)] Published Mon Apr 06, 2015

]]>Most of the previously suggested scenarios for the realization of Weyl semimetal on a pyrochlore lattice require breaking of time-reversal symmetry. In this study the authors show that spontaneous deformations of the crystal that break the inversion symmetry can stabilize this phase as well. They demonstrate that in the temperature-elasticity phase diagram Weyl semimetal shows a reentrant behavior.

[Phys. Rev. B 91, 165105] Published Mon Apr 06, 2015

]]>Semiconductor nanostructures, such as arrays of Si nanowires, are promising candidates for photonic and photovoltaic applications where light management and light trapping abilities are essential. A significant aspect for the development of such functionality is understanding the electromagnetic field distribution around the nanostructures. In this Rapid Communication, a collaboration of researchers from Toulouse and Grenoble use nonlinear microscopy on isolated silicon nanowires in order to study the local electromagnetic field morphology. They find that the second harmonic generation yield in Si nanowires can be strongly enhanced compared to bulk silicon.

[Phys. Rev. B 91, 121416(R)] Published Tue Mar 31, 2015

]]>Density functional theory calculations of the electronic properties of graphene-hexagonal indium telluride superlattices predicts two inequivalent geometrical structures that are almost degenerate in energy. These structures give rise to either gapped states in Kekule phase or gapless states in reconstructed graphene Dirac cones. The results of this study will be useful for exploring the possibility of many-body instabilities in two-dimensional systems.

[Phys. Rev. B 91, 121417(R)] Published Tue Mar 31, 2015

]]>Magnetoelastic coupling describes the interaction between the magnetic degrees of freedom of a material and its strain. This Rapid Communication presents a microscopic model of magnetoelasticity in which all parameters are derived from first-principles calculations. In application to multiferroic materials, the model reveals a new contribution to the electric polarization that appears as a combination of the magnetoelastic and piezoelectric effects. Surprisingly, in the prototypical multiferroic material BiFeO${}_{3}$ the new effect is responsible for a significant share of the total polarization and exceeds the known ionic and electronic contributions.

[Phys. Rev. B 91, 100405(R)] Published Mon Mar 30, 2015

]]>The electron-phonon scattering dominated heat dissipation is difficult to observe in graphene due to the role of impurities in scattering processes. Owing to the suppression of flexural-mode-induced supercollisions in suspended bilayer graphene, the authors of this paper are able to demonstrate that the intrinsic electron-optical phonon coupling governs the heat flow in suspended bilayer graphene samples.

[Phys. Rev. B 91, 121414(R)] Published Fri Mar 27, 2015

]]>Chiral crystals come in left- and right-handed forms. Methods for using electron diffraction to determine crystal chirality have heretofore required the use of multiple scattering and depended sensitively on the sample thickness. Here it is shown that these constraints can be removed with the use of electron vortex beams (which carry orbital angular momentum) in a transmission electron microscope. In accordance with theoretical expectation, the chirality of a sample of Mn${}_{2}$Sb${}_{2}$O${}_{7}$ is experimentally determined.

[Phys. Rev. B 91, 094112] Published Thu Mar 26, 2015

]]>Gd${}_{1-x}$Tb${}_{x}$MnO${}_{3}$ oxides are characterized by two main competing states that exhibit both ferroelectric and multiferroic ordering. Both states involve cycloidal magnetic order that drives ferroelectricity. In their new article, a collaboration of researchers from Japan discovered that exposure of Gd${}_{0.5}$Tb${}_{0.5}$MnO${}_{3}$ to x-ray irradiation induces a reversible transition into a new hidden state, which is also characterized by cycloidal order, but with a different modulation wave vector. The ability to manipulate the state with x-rays suggests a novel route for photocontrol of multiferroic materials.

[Phys. Rev. B 91, 100403(R)] Published Tue Mar 24, 2015

]]>Using infrared excitation at cryogenic temperatures in thin films of GeSbTe compounds, the authors observe persistent-photoconductivity (charge generation by exposure to light without change of stoichiometry) in a material that also exhibits intrinsic electron-glass behavior and has high carrier concentration.

[Phys. Rev. B 91, 094204] Published Mon Mar 23, 2015

]]>Using high-resolution specific heat and SQUID magnetization measurements, this group studies the thermodynamic phase transitions of BaFe${}_{2}$(As${}_{1-x}$P${}_{x}$)${}_{2}$ ($x$=0.0, 0.3). The experiments, assisted by theoretical modeling, show that there is no additional ${2}^{n\phantom{\rule{0}{0ex}}d}$ order “true” nematic phase transition at temperatures above the conventional antiferromagnetic/structural transition.

[Phys. Rev. B 91, 094512] Published Mon Mar 23, 2015

]]>A collaboration of researchers from Japan and France present a comprehensive study of phonon lifetimes and thermal conductivity for 33 zincblende- and wurtzite compounds using linearized phonon Boltzmann equation and first-principles anharmonic phonon calculations. The software that the authors created for this study will be released as an open source package and should be of help in the search of new materials for thermoelectric applications.

[Phys. Rev. B 91, 094306] Published Fri Mar 20, 2015

]]>This European research team reports the first observation of two-photon lasing in a superconducting circuit consisting of a pair of flux qubits strongly coupled to a coplanar waveguide.

[Phys. Rev. B 91, 104516] Published Thu Mar 19, 2015

]]>The emission linewidth is a key figure of merit for a quantum emitter. This paper reports on the possibility of reducing the spectral linewidth of single-wall carbon nanotubes. It demonstrates an order of magnitude narrower linewidths compared to the available data due to the enhanced crystalline quality of the carbon nanotubes synthesized by using a laser ablation technique.

[Phys. Rev. B 91, 121410(R)] Published Wed Mar 18, 2015

]]>For chiral topological phases there exist analytical proofs of a one-to-one correspondence between the low lying spectrum of edge states and that of the entanglement spectrum. Whether or not such an edge-entanglement spectrum correspondence could apply to non-chiral phases has been unclear. Here it is shown that in the Wen-plaquette model, a non-chiral ${Z}_{2}$ topological phase, such a correspondence is exact in the absence of perturbations. While no such correspondence exists in the case of a general perturbation, the correspondence can be shown to apply for perturbations restricted to be translation invariant along the edge/entanglement cut.

[Phys. Rev. B 91, 125119] Published Wed Mar 11, 2015

]]>The electronic band structure of monolayer V${}_{2}$O${}_{5}$ is examined in detail via quasiparticle self-consistent $G\phantom{\rule{0}{0ex}}W$ calculations. There is much interest currently for such layered systems, especially compared to the bulk. Sophisticated calculations like the ones done here can provide key information on the reasons why DFT calculations significantly overestimate or underestimate the band gap in such materials, a perennial issue. The lattice polarization is the major missing ingredient responsible for the discrepancy in this system.

[Phys. Rev. B 91, 125116] Published Tue Mar 10, 2015

]]>The first comprehensive study is made of the exciton dynamics and spin-relaxation processes in isoelectronic centers in GaAs, single excitons bound to two nitrogen atoms. Such atomic defects may offer advantageous properties for quantum information applications over the more established quantum dots and NV centers in diamond. Time-resolved spectroscopy is coupled with a unique analytical model.

[Phys. Rev. B 91, 115201] Published Mon Mar 09, 2015

]]>There is interest in what happens to ultrashort light pulses propagating through a quantum-dot semiconductor optical amplifier waveguide. In this experiment, the influence of nonresonant propagation effects, such as linear dispersion, two-phonon absorption, and Kerr-like, on the intensity and frequency profile of the pulses is shown to be strong enough that they must be included in any modeling.

[Phys. Rev. B 91, 115304] Published Mon Mar 09, 2015

]]>Whether the non-Fermi-liquid behavior of fermionic systems, developing in the proximity of a quantum critical point, is stable or not toward the formation of Cooper pairs is an interesting and challenging open question in the physics of strongly correlated systems. In this new and interesting contribution to the field, the authors study systems where the non-Fermi-liquid behavior arises as a result of the interaction of a gapless bosonic mode with fermions in the vicinity of the Fermi surface.

[Phys. Rev. B 91, 115111] Published Wed Mar 04, 2015

]]>Recent experiments in ultracold atoms and photonic systems have realized lattice models with artificial gauge fields. Here the authors introduce a bosonic version of the Haldane Hubbard Hamiltonian on the honeycomb lattice and use several analytical and numerical methods to uncover a consistent picture of the phase diagram. Three distinct phases are found: chiral superfluid, uniform superfluid, and a plaquette Mott insulator, all of which should be accessible to future experiments.

[Phys. Rev. B 91, 094502] Published Tue Mar 03, 2015

]]>Using a nonequilibrium dynamical mean-field theory the authors study relaxation of a hot-electron distribution coupled to optical phonons. Their main interest is in the adiabatic regime of phonon frequencies smaller than the electronic bandwidth and in an extended analysis of photoemission spectra. In this limit initial coherent phonon oscillations become strongly damped, leaving the system in a mixture of excited polaron states and metastable delocalized states.

[Phys. Rev. B 91, 104301] Published Tue Mar 03, 2015

]]>Nonequilibrium dynamics of interacting quantum many-body physics has recently attracted great attention. The authors address here the nonequilibrium dynamics of a single electron interacting through a Holstein-like coupling with dispersionless phonons on a one dimensional lattice. Using diagonalization in a limited functional space, they identify two different regimes: (1) the relaxation regime where, during a characteristic time scale, a net energy is transferred between the electronic and the phononic subsystem; and (2) the stationary regime, characterized by zero energy transfer and by persisting coherent oscillations in the dynamics of observables.

[Phys. Rev. B 91, 104302] Published Tue Mar 03, 2015

]]>By investigating transport and structural properties of KFe${}_{2}$As${}_{2}$ under pressures up to 33 GPa, this group reveals the presence of two superconducting phases that appear distinct, and each showing strong enhancements in their transition temperature as a function of pressure. The second, higher-${T}_{c}$ phase abruptly appears upon collapse of the tetragonal structure at higher pressures.

[Phys. Rev. B 91, 060508(R)] Published Fri Feb 27, 2015

]]>In this work the authors present a novel mechanism for interfacial superconductivity which has been observed in many materials including high-${T}_{c}$ superconductors. The suggested mechanism is based on an interplay between competing order parameters: superconducting order parameter, and charge- or spin-density wave.

[Phys. Rev. B 91, 064511] Published Fri Feb 27, 2015

]]>This paper presents a comprehensive study of the interplay of Anderson localization and topological phase transitions in five symmetry classes that allow topological insulators in one dimension.

[Phys. Rev. B 91, 085429] Published Fri Feb 27, 2015

]]>There is great interest in understanding the physics of magnetic ordering and electronic transport in materials of reduced dimensionality with strong spin-orbit coupling. This paper presents magnetotransport measurements of Fe${}_{0.28}$TaS${}_{2}$ single crystals, which are found to exhibit very large magnetoresistance (MR) for magnetic fields along the easy axis. The authors believe that such a large MR arises from spin disorder scattering and propose to use this mechanism as a design principle for materials with large MR. Further tests are needed to fully rule out contributions from a more conventional anisotropic MR mechanism.

[Phys. Rev. B 91, 054426] Published Thu Feb 26, 2015

]]>Transparent conducting oxides, such as In${}_{2}$O${}_{3}$, are optically transparent wide band gap semiconductors with high electrical conductivity and are used in applications such as transparent electrical circuits and flat panel displays. Some previous research has argued that conductivity in In${}_{2}$O${}_{3}$ is caused mainly by oxygen vacancies, as in other transparent conducting oxides. Using infrared absorbtion spectroscopy on single-crystal In${}_{2}$O${}_{3}$, the authors show that, consistent with theory, interstital hydrogen forms shallow donors, which make an important contribution to the $n$-type conductivity.

[Phys. Rev. B 91, 075208] Published Tue Feb 24, 2015

]]>Accurate nanoscale atomistic treatment of semiconductor surfaces, together with accurate microscale treatment of electronic effects induced in the semiconductor near-surface region, is crucial for a very large range of issues in modern electronics. However, this has been a difficult challenge for modern computational materials science. In this paper, this goal is achieved by means of a new multiscale approach that couples seamlessly short-range quantum mechanical effects with long-range electrostatic effects. The usefulness of this approach is demonstrated on a variety of silicon surfaces.

[Phys. Rev. B 91, 075311] Published Tue Feb 24, 2015

]]>The authors use photoluminescence- and electrically-detected magnetic resonance spectroscopies to trace and characterize triplet exciton states in lightly fullerene-doped polymers. This approach can provide an improved analysis of charge excitations and their spin dependent interactions in organic electronics devices, in particular organic light emitting diodes, with the potential to enhance their performance.

[Phys. Rev. B 91, 085309] Published Mon Feb 23, 2015

]]>Fractional Quantum Hall (FQH) wave functions are usually obtained in a first-quantized language, using special properties of analyticity of the lowest Landau level (LLL) wave functions. Unfortunately, this formalism is not directly applicable to several systems different from the LLL, such as the recently discovered fractional Chern insulators. Introducing a second-quantized formalism represents an important step towards a new understanding of FQH wave functions in terms of the guiding center degrees of freedom only. In this paper, the authors present several applications of the formalism, including an explicit derivation of the second-quantized version of Read’s string order parameter for the Laughlin state.

[Phys. Rev. B 91, 085115] Published Fri Feb 20, 2015

]]>An important theoretical approach to topologically ordered phases is based on topological field theories. These directly incorporate such important features as the absence of bulk excitations, ground state degeneracy on topologically nontrivial manifolds, and dynamical edge states. The authors construct an effective field theory for a two-dimensional spinless $p$-wave superconductor that describes the topological properties of the bulk state, and also provides a model for the subgap states at vortex cores and edges.

[Phys. Rev. B 91, 075116] Published Thu Feb 19, 2015

]]>In type-II multiferroics ferroelectricity is driven by magnetism, and the coupling between the two orders is generally larger than in conventional multiferroic materials. However, a critical problem that needs to be overcome for type-II multiferroics is that their polarization is far too low to be useful for applications. In this Rapid Communication, a group of researchers from Osaka University, Japan, demonstrate that in three prototypical manganites (TbMnO${}_{3}$, DyMnO${}_{3}$, and GdMnO${}_{3}$) magnetic field can induce giant changes in polarization under high pressure. In the gadolinium compound, the change they have observed reaches the record high value of 1.3 $\mu $C/cm${}^{2}$ among the spin-driven multiferroics.

[Phys. Rev. B 91, 081107(R)] Published Wed Feb 18, 2015

]]>Using pump-probe spectroscopy a Japanese research team studies the physical properties of an intrinsic topological insulator material. Monitoring initial non-equilibrium photo-excitation they find that Auger recombination is an essential relaxation mechanism, in addition to thermalization, cooling, and population relaxation and dominates for higher carrier densities.

[Phys. Rev. B 91, 085306] Published Tue Feb 17, 2015

]]>Site-controlled and scalable growth of quantum dots in semiconductors is an active area of research important for a number of applications. In one approach the position of the quantum dots is determined by artificially engineered local strain fields in the growth surface. A more complete and accurate understanding of the growth process depends on the ability to accurately the strain, and this is what the authors pursue in this article using high-precision dark-field electron holography.

[Phys. Rev. B 91, 075306] Published Thu Feb 12, 2015

]]>The authors study the phenomena of many-body localization in a random field Heisenberg chain. In this paper the authors use a shift-inverse exact diagonalization approach that allows them to study the mid-spectrum spectral properties of the model for system sizes of up to N=22. This has allow the authors to identify the many-body localization edge.

[Phys. Rev. B 91, 081103(R)] Published Mon Feb 09, 2015

]]>This paper studies studies the spin-1/2 XXZ antiferromagnet on a triangular lattice using a density matrix renormalization group. The authors study the phase diagram of this model as a function of magnetic field and spin anisotropy.

[Phys. Rev. B 91, 081104(R)] Published Mon Feb 09, 2015

]]>The optical response of photoinduced charge-carrier plasmas in silicon are measured over a wide range of excitation densities in a pump-probe experiment. By using not just traditional terahertz probe pulses but also terahertz-midinfrared, a better estimate of the charge carrier scattering time is found. A detailed analysis of the early time dynamics in their experiment is also presented.

[Phys. Rev. B 91, 075201] Published Wed Feb 04, 2015

]]>A three-terminal thermoelectric junction is studied theoretically and a counterintuitive result is obtained. The cooling efficiency is increased for configurations when not only one terminal is cooled but also electric power is generated.

[Phys. Rev. B 91, 054302] Published Tue Feb 03, 2015

]]>A theoretical evaluation of the dynamic polarizability of graphene in a photoexcited carrier inversion state shows that graphene can support nonequilibrium plasmons with gain. The authors predict that the experimental observation of plasmon amplification in graphene is possible under realistic conditions. This would help overcome the barriers to using graphene in plasmonics due to plasmon losses.

[Phys. Rev. B 91, 075404] Published Tue Feb 03, 2015

]]>The authors create an unconventional superconducting state in the vicinity of noncollinear ferromagnetic interfaces. In particular, they use Co spin-valve structures to modify the superconducting state of Nb, a conventional superconductor, by the controlled generation of equal spin superconducting triplets from the singlet ground state.

[Phys. Rev. B 91, 060501(R)] Published Mon Feb 02, 2015

]]>A magneto-optical study of flux distributions in superconducting YBCO under various applied crossed-field orientations elucidates the complex nature of magnetic flux cutting, and reveals unusual vortex patterns induced by the interplay between flux-cutting and vortex pinning.

[Phys. Rev. B 91, 014516] Published Fri Jan 30, 2015

]]>Following the authors’ own discovery of superconductivity in quasi-one-dimensional K${}_{2}$Cr${}_{3}$As${}_{3}$, the analogous compound Rb${}_{2}$Cr${}_{3}$As${}_{3}$ is synthesized for the first time in polycrystalline form. Bulk superconductivity emerges at 4.8 K. Further work is needed to verify the nature of the superconducting state.

[Phys. Rev. B 91, 020506(R)] Published Fri Jan 30, 2015

]]>K${}_{2}$Cr${}_{3}$As${}_{3}$ is a newly discovered compound that has a superconducting transition temperature of 6.1 K. Special interest in it stems from the fact that it crystallizes in a hexagonal lattice containing a quasi-one-dimensional chain structure made of (Cr${}_{3}$As${}_{3}$)${}^{2-}$. With careful measurements on single crystals this research team from Iowa State University demonstrates that although the material can be considered to be close to quasi-one-dimensional in a crystallographic sense, the data support a three-dimensional nature with Fermi-liquid-like properties.

[Phys. Rev. B 91, 020507(R)] Published Fri Jan 30, 2015

]]>Using femtosecond laser excitation to melt stripe order in La${}_{1.675}$Eu${}_{0.2}$Sr${}_{0.125}$CuO${}_{4}$, the authors reintroduce $c$-axis coherent coupling and observe the formation and subsequent relaxation of a competing state, which can be induced up to 80 K. In addition, they also find two distinct kinetic regimes above and below the spin-order transition at ${T}_{S\phantom{\rule{0}{0ex}}O}$~25 K.

[Phys. Rev. B 91, 020505(R)] Published Thu Jan 29, 2015

]]>In the context of plasmonic nanolasers, it has been previously recognized that systems with physically extended modes (as opposed to isolated cavity modes) can support lasing, and plasmonic crystals are a platform for such effects. In the present paper the authors present a general study that explores, from a unified perspective, the lasing properties of plasmonic crystals incorporating optically pumped four-level gain media.

[Phys. Rev. B 91, 041118(R)] Published Mon Jan 26, 2015

]]>Hyperuniform disordered materials are a class of photonic solids with a constrained randomness that have short-range order and long-range statistical isotropy. In these materials, calculations suggest a new type of high-Q localization mechanism in optical cavities, that has no analogue in periodic or quasi-periodic photonic crystals.

[Phys. Rev. B 91, 020201(R)] Published Tue Jan 20, 2015

]]>The first direct measurements are reported of the evolution of the thickness-dependent electronic band structure of monolayers of a material of much current interest. Angle-resolved photoemission is performed on the few-layer single-crystal dichalcogenide WSe${}_{2}$, which is in a class of graphene-like semiconductors with a desirable band gap in the visible frequency range. These results strongly support the presence of a predicted transition from an indirect (bulk or bilayer) to direct (one monolayer) band gap. Values are obtained for the effective mass and spin-orbit splitting of few-layer WSe${}_{2}$, parameters which are very important for transport studies and device applications.

[Phys. Rev. B 91, 041407(R)] Published Tue Jan 20, 2015

]]>Optical measurements on highly doped single-layer epitaxial graphene reveal that the photoexcitation of charge carriers leads to an enhancement of the THz transmission. In this paper, the results are explained in terms of the change in the carrier scattering rate due to the optical pump fluence and the THz electric field.

[Phys. Rev. B 91, 035422] Published Fri Jan 16, 2015

]]>Quantum Hall systems are expected to host a variety of exotic phases. In particular 5/2 filling fraction is believed to contain non-Abelian anyons. However, the exact nature of the ground state is sensitive to many factors and is hard to access. In this paper the authors develop a method to take into account scattering between Landau levels and show that, at 5/2 filling, it leads to the stabilization of the so called anti-Pfaffian state.

[Phys. Rev. B 91, 045115] Published Wed Jan 14, 2015

]]>This paper presents a systematic study of the magnetic and superconducting properties of Ba(Fe${}_{0.95}$Co${}_{0.05}$)${}_{2}$As${}_{2}$ as a function of temperature and external magnetic field using neutron scattering and muon spin rotation. Calculations based on the five-band Hubbard Hamiltonian reproduce the physical properties of the coexistence region of Ba(Fe${}_{1-x}$Co${}_{x}$)${}_{2}$As${}_{2}$. Below the superconducting transition temperature the magnetic and superconducting order parameters coexist and compete. An external magnetic field significantly enhances the magnetic order parameter within the superconducting state. This behavior can be caused by the vortices, which in the superconducting state can slow down and locally freeze spin fluctuations.

[Phys. Rev. B 91, 024504] Published Tue Jan 13, 2015

]]>This paper reports an experimental observation of the square root q behavior of $\pi $-plasmons in free-standing graphene. The authors used very high resolution EELS measurements to be able to probe plasmonic excitations in the long wavelength limit.

[Phys. Rev. B 91, 045418] Published Tue Jan 13, 2015

]]>LuFe${}_{2}$O${}_{4}$ is being actively studied in the context of an unconventional electronic ferroelectricity that appears due to charge ordering of $F\phantom{\rule{0}{0ex}}{e}^{2+}$ and $F\phantom{\rule{0}{0ex}}{e}^{3+}$ oxidation states. LuFe${}_{2}$O${}_{4}$ displays a high magneto-electric coupling, giant magnetic coercivity, and other unusual features, some of them highly controversial. In this study a group of researchers from Japan present their XMCD results in pulsed magnetic fields reaching 30 Tesla. Their technique allows them to measure valence-specific magnetization of $F\phantom{\rule{0}{0ex}}{e}^{2+}$ and $F\phantom{\rule{0}{0ex}}{e}^{3+}$ ions above and below the charge-ordering temperature and provides a unique view on the coupling between the charge and spin degrees of freedom in LuFe${}_{2}$O${}_{4}$.

[Phys. Rev. B 91, 014410] Published Mon Jan 12, 2015

]]>The identification of hidden order in URu${}_{2}$Si${}_{2}$ is currently a hot topic in condensed matter physics. By performing a much more detailed lineshape analysis of their own NMR data previously published in PRL, a strong argument is put forward that nematic/orthorhombic distortion is not the primary hidden order parameter and that this parameter may be sensitive to disorder. Many local defects were found, even in the best quality samples.

[Phys. Rev. B 91, 035111] Published Mon Jan 12, 2015

]]>The authors introduce an approach to investigate the spatial distribution of the electrons in InAs nanowires using the anisotropy of low temperature magneto-conduction fluctuations. With this technique, the authors argue that the electrons responsible for transport in the nanowire are distributed through the bulk of the wire as opposed to being confined to the wire’s surface.

[Phys. Rev. B 91, 041302(R)] Published Mon Jan 12, 2015

]]>Ultrafast scattering of highly energetic carriers in semiconductors is of great interest to both basic research and technological development. Using the technique of two-photon photoemission, instead of the more common ultrafast optical spectroscopy, in this study provides the ability to probe the conduction-band electron distributions in energy, momentum, and time on femtosecond to picosecond time scales. Deeper insight is obtained into the physics underlying hot-electron relaxation in InSb, a model system for semiconductors with a narrow band gap.

[Phys. Rev. B 91, 045201] Published Mon Jan 12, 2015

]]>A collaboration of authors from Switzerland, Estonia, and Germany present the results of neutron diffraction experiments, AC magnetometry and specific heat measurements for an organic quantum magnet NiCl${}_{2}\cdot $4SC(NH${}_{2}$)${}_{2}$ (often abbreviated as DTN).For more than a decade, DTN has been considered as a prominent candidate for BEC realization in quantum magnets. However, the presented results suggest that previous interpretations of data were strongly affected by distribution of transition magnetic fields in the samples, and that the critical exponents describing the transition are incompatible with the BEC universality class.

[Phys. Rev. B 91, 014406] Published Fri Jan 09, 2015

]]>Antireflective acoustic coatings for hiding submarines and other watercraft could be made much thinner than those in use today.

[Phys. Rev. B 91, 020301(R)] Published Tue Jan 06, 2015

]]>By means of alloying appropriate amounts of MnNiSi and MnFeGe, materials are found that undergo a paramagnetic to ferromagnetic transition close to room temperature, accompanied by a huge volume change. Thanks to this volume change, application of moderate pressures leads to a remarkable enhancement of the magnetocaloric response. Work like this may open new opportunities in the development of new solid-state magnetic refrigeration devices.

[Phys. Rev. B 91, 020401(R)] Published Mon Jan 05, 2015

]]>The invention and development of memory devices are important tasks for facilitating continued innovation in the field of information technology. The authors achieve repeatable switching between a high-resistivity charge-crystalline (or charge-ordered) state and a low-resistivity quenched charge glass via both optical and electrical heating in an organic conductor, $\theta $-(BEDT-TTF)${}_{2}$$X$. They observe switching that is one order of magnitude faster in another isostructural organic conductor that requires faster cooling ($>{10}^{3}$ K/s) to kinetically avoid charge crystallization, indicating that the material’s critical cooling rate can be a useful guideline for pursuing a faster “correlated-electron phase-change memory (PCM)”. These results establish a clear case whereby practically stable glassy electronic states hidden behind long-range ordered states can be uncovered by adopting hitherto-untried quenching rates and thus underlies a new class of non-volatile PCM.

[Phys. Rev. B 91, 041101(R)] Published Mon Jan 05, 2015

]]>Using modern thin film growth techniques, and performing structural, magnetic, optical and electrical transport measurements on YbN thin films, the authors show that these films are antiferromagnetic and semiconducting, unlike other rare-earth nitrides that are either para- or ferromagnetic.

[Phys. Rev. B 90, 245206] Published Mon Dec 29, 2014

]]>Recent spectroscopic imaging experiments have showed evidence of one-dimensional topological superconductivity and Majorana bound states in fabricated iron atomic chains on the surface of lead. In this follow-up paper the authors present an extensive theoretical analysis of ferromagnetic atomic chains deposited on a conventional superconductor.

[Phys. Rev. B 90, 235433] Published Wed Dec 24, 2014

]]>Strongly correlated fermionic systems have been one of the most studied fields in condensed matter theory. The competition between Coulomb-repulsion and kinetic energy leads to a manifold of individual phases, especially in lower dimensions. Famous examples are Luttinger liquids in one dimensions, Mott-insulators or topological phases such as spin liquids. Recently a new class of non-trivial insulators has been introduced, the fragile Mott insulator (FMI). In this paper the authors extend the concept of an FMI to the case of ring-shaped molecules and study the interplay between symmetry, strong correlations as well as strong interactions which ultimately determine the electronic structure of the system.

[Phys. Rev. B 90, 245142] Published Tue Dec 23, 2014

]]>This paper analyzes the edge states and spontaneous edge current of a chiral $p$-wave superconductor. In particular, the authors show with both a lattice model and a quasiclassical approach that the edge state dispersion and current can be strongly affected by the orientation of the surface.

[Phys. Rev. B 90, 220511(R)] Published Mon Dec 22, 2014

]]>The dual boson method provides a systemic way to do diagrammatic expansion on top of extended dynamical mean-field theory (EDMFT) and can be very useful for the computational research on many strongly correlated systems. The authors present the first application of the method and give a very detail description for both its analytical basis and its numeral realization.

[Phys. Rev. B 90, 235135] Published Mon Dec 22, 2014

]]>The study of Symmetry-Protected Topological (SPT) phases has become a very active research fields in condensed matter with ramifications to a wide variety of areas such as quantum computation, photonics and spintronics. In this paper the authors propose a new method to classify interacting bosonic symmetry-protected topological phases in arbitrary spatial dimensions.

[Phys. Rev. B 90, 235137] Published Mon Dec 22, 2014

]]>How well the various approximate exchange-correlation functionals in density functional theory capture the 3D to 2D crossover, observed, for example, for plasmon modes in quantum wells that approach the strictly two-dimensional limit? This work, inspired by several ground-state DFT studies performed a few years ago, examines this question in the dynamical case, using time-dependent DFT, and reveals that the (semi)local 3D exchange eventually breaks down, but remains valid for most practical applications. Also, it demonstrates that nonlocal, orbital-dependent functionals are the appropriate way to handle the dimensional crossover.

[Phys. Rev. B 90, 245304] Published Mon Dec 22, 2014

]]>By taking into account quantum fluctuations, the authors develop a theory of the interactions between spinons and photons in quantum spin ice.

[Phys. Rev. B 90, 214430] Published Thu Dec 18, 2014

]]>This paper provides an experimental description and theoretical explanation of how disorder affects electronic transport in antiferromagnetic thin films. The authors find a quantum correction to the conductivity which survives to high disorder strength because of a high rate of inelastic scattering of electrons off of gapped antiferromagnetic spin waves. The data provide first-time estimates of the spin-wave energy gap and exchange energy derived solely from transport measurements. The focus on the unexplored effect of antiferromagnetism on electronic transport provides new perspectives on the role of electronic transport and spin alignment in disordered magnetic systems.

[Phys. Rev. B 90, 214429] Published Wed Dec 17, 2014

]]>The authors study a kagome artificial spin ice cooled from above its Curie temperature. They argue that the system after cooling, while appearing locally to be in the expected spin ice 2 phase, globally seems to be in some non-equilibrium state.

[Phys. Rev. B 90, 220407(R)] Published Wed Dec 17, 2014

]]>A complete theoretical methodology of the interactions between chiral molecules and the evanescent fields of localized surface plasmons generated in a metallic nanostructure of arbitrary shape. The calculations confirm various previous results on the enhancement of the absorption of light and subsequent circular dichroism by surface plasmons. They also predict a chirality-dependent absorption arising from the metallic nanostructure illuminated with linearly polarized light.

[Phys. Rev. B 90, 235424] Published Mon Dec 15, 2014

]]>Low-temperature neutron diffraction and field-dependent heat capacity measurements for the monazite GdPO${}_{4}$ compound shows some very interesting properties. In particular it displays a large magnetocaloric effect and it shows promise in applications for cooling at very low temperatures.

[Phys. Rev. B 90, 214423] Published Fri Dec 12, 2014

]]>A detailed material-dependent analysis of the skew scattering mechanism in dilute alloys is presented for the first time for the anomalous Hall effect. In addition, the authors examine the spin Hall effect in ferromagnets from a first-principles perspective shedding light on its magnitude and on its relation to the anomalous Hall effect. Also, three up-to-date numerical methods are compared to each other demonstrating the subtlety of the effects under investigation. Small changes in the theoretical analysis or the experimental methods can, under certain conditions, influence the results drastically. The authors provide guidelines to both theoreticians and experimentalists as to where special attention has to be paid.

[Phys. Rev. B 90, 220403(R)] Published Mon Dec 08, 2014

]]>For a given many-body Hamiltonian, can a wavefunction in the wrong phase yield an arbitrarily good variational approximation to the true ground state energy density? The author discusses systems for which the answer is positive and outlines other cases where the Hamiltonian is expected to be variationally robust.

[Phys. Rev. B 90, 245116] Published Mon Dec 08, 2014

]]>By exploiting the high spatial resolution of scanning tunneling microscopy/spectroscopy at sub-Kelvin temperatures, the authors investigate superconductivity in the prototypical Pb/Ag/Si(111) system. In this paper they present the first experimental consideration of the effect of an external magnetic field on the spatially-dependent extension of superconductivity across a nanostructure superconductor-metal boundary. This study reveals the first quantitative data on the interplay between induced superconductivity in a normal metal and magnetic field with nanometer spatial resolution.

[Phys. Rev. B 90, 220507(R)] Published Fri Dec 05, 2014

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