We present highly subwavelength magnetic metamaterials designed for operation at radio frequencies (rf's). A dual-layer design consisting of independent planar spiral elements enables the experimental demonstration of a unit cell size (a) that is ∼700 times smaller than the resonant wavelength (λ₀)....

[Phys. Rev. B 85, 201104] Published Wed May 16, 2012

The phantom force is an apparently repulsive force, which can dominate the atomic contrast of an AFM image when a tunneling current is present. We described this effect with a simple resistive model, in which the tunneling current causes a voltage drop at the sample area underneath the probe tip. Be...

[Phys. Rev. B 85, 195426] Published Mon May 14, 2012

We present ac susceptibility and specific-heat measurements taken on samples of LiHo_xY_1−xF₄ in the dilute limit: x=0.018, 0.045, 0.080, and 0.12. Susceptibility measurements show glassy behavior including wide absorption spectra that continually broaden with decreasing temperature. Dynamical scaling...

[Phys. Rev. B 85, 184415] Published Mon May 14, 2012

The competition between intertube hopping processes and density-density interactions is investigated in one-dimensional quantum dipolar bosons systems of N coupled tubes at zero temperature. Using a phenomenological bosonization approach, we show that the resulting competition leads to an exotic qua...

[Phys. Rev. B 85, 195121] Published Thu May 10, 2012

We show that a three-dimensional topological insulator doped with magnetic impurities in the bulk can have a regime where the surface is magnetically ordered but the bulk is not. This is in contrast to conventional materials where bulk ordered phases are typically more robust than surface ordered ph...

[Phys. Rev. B 85, 195119] Published Thu May 10, 2012

We derive an approximate analytical solution of the self-consistency equations of the bosonic dynamical mean-field theory (B-DMFT) in the strong-coupling limit. The approach is based on a linked-cluster expansion in the hybridization function of normal bosons around the atomic limit. The solution is...

[Phys. Rev. B 85, 205115] Published Wed May 09, 2012

Employing a classical density-functional description of liquid environments, we introduce a rigorous method for the diffusion quantum Monte Carlo calculation of free energies and thermodynamic averages of solvated systems that requires neither thermodynamic sampling nor explicit solvent electrons. W...

[Phys. Rev. B 85, 201102] Published Tue May 08, 2012

Using ultrahigh magnetic fields up to 170 T and polarized midinfrared radiation with tunable wavelengths from 9.22 to 10.67 μm, we studied cyclotron resonance in large-area graphene grown by chemical vapor deposition. Circular polarization dependent studies reveal strong p-type doping for as-grown g...

[Phys. Rev. B 85, 205407] Published Fri May 04, 2012

We systematically investigate magnetic reversal of permalloy islands in a square spin-ice geometry with in situ Lorentz microscopy. Differential phase imaging reveals the presence of a flux channel similar to a Dirac string between the magnetic charge monopoles during the reversal. Analysis of the p...

[Phys. Rev. B 85, 180402] Published Fri May 04, 2012

Superlattices (SLs) in monolayer and bilayer graphene, formed by spatially periodic potential variations, lead to a modified bandstructure with extra finite-energy and zero-energy Dirac fermions with tunable anisotropic velocities. We theoretically show that transport in a weak perpendicular (orbita...

[Phys. Rev. B 85, 195404] Published Thu May 03, 2012

It has been suggested that after being gapped by a small symmetry-breaking field, the Majorana quasiparticles localized on the surface of a class DIII topological insulator will exhibit a thermal Hall effect that arises from a gravitational Chern-Simons term. We critically examine this idea, and arg...

[Phys. Rev. B 85, 184503] Published Thu May 03, 2012

A number of recent experiments have used torsional oscillators to study the behavior of solid helium. The oscillator frequencies increased at temperatures below 200 mK, an effect attributed to decoupling of a fraction of the helium mass—the signature of a “supersolid” phase. However, helium's shear ...

[Phys. Rev. B 85, 180501] Published Thu May 03, 2012

We have experimentally studied the nonlinear nature of electrical conduction in monolayer graphene devices on silica substrates. This nonlinearity manifests itself as a nonmonotonic dependence of the differential resistance on applied dc voltage bias across the sample. At temperatures below ∼70 K, t...

[Phys. Rev. B 85, 161411] Published Mon Apr 30, 2012

We investigate the pairing in iron pnictides in the coexistence phase, which displays both superconducting and antiferromagnetic orders. By solving the pairing problem on the Fermi surface reconstructed by long-range magnetic order, we find that the pairing interaction necessarily becomes angle depe...

[Phys. Rev. B 85, 144527] Published Mon Apr 30, 2012

We study the Anderson impurity problem in a mesoscopic setting, namely the “Anderson box,” in which the impurity is coupled to finite reservoir having a discrete spectrum and large sample-to-sample mesoscopic fluctuations. Note that both the weakly coupled and strong coupling Anderson impurity probl...

[Phys. Rev. B 85, 155455] Published Fri Apr 27, 2012

Electron doping of a 122-type iron pnictide BaFe₂As₂ by substituting the Ba site with an aliovalent ion (indirect doping), which had been unsuccessful by conventional solid-state synthesis methods, was achieved by a nonequilibrium film growth process. The substitution with La was substantiated by a ...

[Phys. Rev. B 85, 140516] Published Fri Apr 27, 2012

The Heusler-derived multiferroic alloy Ni_50−xCo_xMn₄₀Sn₁₀ has recently been shown to exhibit, at just above room temperature, a highly reversible martensitic phase transformation with an unusually large magnetization change. In this work the nature of the magnetic ordering above and below this transf...

[Phys. Rev. B 85, 134450] Published Fri Apr 27, 2012

The low-temperature magnetic behavior of the double-layered ruthenate Sr₃Ru₂O₇, as grown from a eutectic Sr₂RuO₄-Sr₃Ru₂O₇ system, was investigated via zero- and transverse-field muon-spin rotation. The gradual increase of the muon relaxation rate observed below 2.5 K, even in the absence of applied ...

[Phys. Rev. B 85, 134527] Published Thu Apr 26, 2012

Highly sp³-bonded, nearly hydrogen-free carbon-based materials can exhibit extremely low friction and wear in the absence of any liquid lubricant, but this physical behavior is limited by the vapor environment. The effect of water vapor on friction and wear is examined as a function of applied norma...

[Phys. Rev. B 85, 155448] Published Wed Apr 25, 2012

We investigate the magnetic polarization of the Ir 5d dopant states in the pnictide superconductor Ba(Fe_1−xIr_x)₂As₂ with x=0.027(2) using Ir L₃ edge x-ray resonant magnetic scattering (XRMS). Despite the fact that doping partially suppresses the antiferromagnetic transition, we find that magnetic or...

[Phys. Rev. B 85, 140514] Published Wed Apr 25, 2012

Magnetic properties of YbAl₃C₃ with the hexagonal ScAl₃C₃-type structure have been investigated by the magnetization (M) and specific-heat (C) measurements under magnetic fields (H). YbAl₃C₃ is reported to show a spin-gap state, which is considered to be ascribed to a magnetic dimer formed in the or...

[Phys. Rev. B 85, 144416] Published Fri Apr 20, 2012

We report a systematic study of the hyperfine interaction between the electron spin of a single nitrogen-vacancy (NV) defect in diamond and nearby ¹³C nuclear spins, by using pulsed electron-spin resonance spectroscopy. We isolate a set of discrete values of the hyperfine coupling strength ranging f...

[Phys. Rev. B 85, 134107] Published Fri Apr 20, 2012

The general Lagrange-Euler formalism for the three memory circuit elements, namely, memristive, memcapacitive, and meminductive systems, is introduced. In addition, mutual meminductance, i.e., mutual inductance with a state depending on the past evolution of the system, is defined. The Lagrange-Eule...

[Phys. Rev. B 85, 165428] Published Fri Apr 13, 2012

The spin interaction between an electron and nuclei was investigated optically in a single self-assembled InAlAs quantum dot (QD). In spin dynamics at the initial stage, the fluctuation of nuclear field and the resulting electron spin relaxation time play a crucial role. We examined a positively cha...

[Phys. Rev. B 85, 155315] Published Fri Apr 13, 2012

We use self-consistent quantum transport theory to investigate the influence of electron-electron interactions on interlayer transport in semiconductor electron bilayers in the absence of an external magnetic field. We conclude that, even though spontaneous pseudospin order does not occur at zero fi...

[Phys. Rev. B 85, 165424] Published Thu Apr 12, 2012

Periodically driven systems, which can be described by Floquet theory, have been proposed to show characteristic behavior that is distinct from static Hamiltonians. Floquet theory proposes to describe such periodically driven systems in terms of states that are indexed by a photon number in addition...

[Phys. Rev. B 85, 155425] Published Thu Apr 12, 2012

The preparation of a coherent heavy-hole spin via ionization of a spin-polarized electron-hole pair in an InAs/GaAs quantum dot in a Voigt geometry magnetic field is experimentally investigated. For a dot with a typical bright-exciton fine-structure splitting of 17 μeV, the fidelity of the spin prep...

[Phys. Rev. B 85, 155310] Published Wed Apr 11, 2012

A time-reversal invariant Kitaev-type model is introduced in which spins (Dirac matrices) on the square lattice interact via anisotropic nearest-neighbor and next-nearest-neighbor exchange interactions. The model is exactly solved by mapping it onto a tight-binding model of free Majorana fermions co...

[Phys. Rev. B 85, 155119] Published Wed Apr 11, 2012

The coupling of angstrom-sized electron probes with spin-polarized electronic transitions shows that the inelastically scattered probe electron is in a mixed state containing electron vortices with nonzero orbital angular momentum. These electrons create an asymmetric intensity distribution in energ...

[Phys. Rev. B 85, 134422] Published Wed Apr 11, 2012

We study a lattice model of interacting loops in three dimensions with a 1/r² interaction. Using Monte Carlo methods, we have found that the phase diagram contains a line of second-order phase transitions between a phase where the loops are gapped and a phase where they proliferate. The correlation ...

[Phys. Rev. B 85, 144303] Published Tue Apr 10, 2012