We propose a hole-doped molybdenum disulfide (${\mathrm{MoS}}_2$) superconducting spin valve (F/S/F) hybrid structure in which the Andreev reflection process is suppressed for all incoming waves with a determined range of the chemical potential in ferromagnetic (F) region and the cross-conductance in the right F region depends crucially on the configuration of magnetizations in the two F regions. Using the scattering formalism, we find that the transport is mediated purely by elastic electron cotunneling (CT) process in a parallel configuration and changes to the pure crossed Andreev reflection (CAR) process in the low-energy regime, without fixing of a unique parameter, by reversing the direction of magnetization in the right F region. This suggests both valley- and spin-switch effects between the perfect elastic CT and perfect CAR processes and makes the nonlocal charge current to be fully valley- and spin-polarized inside the right F region where the type of the polarizations can be changed by reversing the magnetization direction in the right F region. We further demonstrate that the presence of the strong spin-orbit interaction $\lambda$ and an additional topological term ($\beta$) in the Hamiltonian of ${\mathrm{MoS}}_2$ result in an enhancement of the charge conductance of the CT and CAR processes and make them to be present for long lengths of the superconducting region. Besides, we find that the thermal conductance of the structure with a small length of the highly doped superconducting region exhibits linear dependence on the temperature at low temperatures, whereas it enhances exponentially at higher temperatures. In particular, we demonstrate that the thermal conductance versus the strength of the exchange field ($h$) in F region displays a maximum value at $h<\lambda$, which moves towards larger exchange fields by increasing the temperature.

Li's paper [Phys. Rev. B 85, 235407 (2012)] presents density functional theory (DFT) results of stress as a function of different strain states. The work of Cooper et al. [Phys. Rev. B 87, 035423 (2013)] performs the same DFT calculations as part of an investigation into the nonlinear elastic properties of ${\mathrm{MoS}}_2$. Some of the DFT results of Li are substantially different from our recently published paper, Cooper et al. [Phys. Rev. B 87, 035423 (2013)]. Although both papers agree on states of equibiaxial stress, there is substantial disagreement on states of uniaxial tensile stress. In this Comment we show that our DFT computations are properly executed and consistent across three different DFT codes, including the one used by Li.

In the Comment, Cooper et al. pointed out a disagreement between two recent density functional theory (DFT) studies ([Li, Phys. Rev. B 85, 235407 (2012)] and [Cooper et al., Phys. Rev. B 87, 035423 (2013)]) on the uniaxial tensile stress as a function of the applied strain along the zigzag $\left(x\right)$ and armchair $\left(y\right)$ directions of single-layer ${\mathrm{MoS}}_2$. We show here that it is the in-plane atomic relaxation under the applied uniaxial tensile stress, rather than the errors in the execution of the DFT calculation, that leads to the discrepancy. Furthermore, through new analysis, we show that our original conclusion that the tensile strength of single-layer ${\mathrm{MoS}}_2$ is dictated by out-of-plane soft-mode phonon instability under the biaxial tension and the uniaxial tension along the armchair direction is still valid when the in-plane atomic relaxation is considered.

A detailed understanding of the vibrational heat transfer mechanisms between solids is essential for the efficient thermal engineering and control of nanomaterials. We investigate the frequency dependence of anharmonic scattering and interfacial thermal conduction between two acoustically mismatched solids in planar contact by calculating the spectral decomposition of the heat current flowing through an interface between two materials. The calculations are based on analyzing the correlations of atomic vibrations using the data extracted from nonequilibrium molecular dynamics simulations. Inelastic effects arising from anharmonic interactions are shown to significantly facilitate heat transfer between two mass-mismatched face-centered-cubic lattices even at frequencies exceeding the cutoff frequency of the heavier material due to (i) enhanced dissipation of evanescent vibrational modes and (ii) frequency-doubling and frequency-halving three-phonon energy transfer processes at the interface. The results provide substantial insight into interfacial energy transfer mechanisms, especially at high temperatures, where inelastic effects become important and other computational methods are ineffective.

Neutron diffraction measurements on a single crystal of ${\mathrm{CeGe}}_{1.76}$ reveal a complex series of magnetic transitions at low temperature. At $T_{\mathrm{N}}\approx 7$ K, there is a transition from a paramagnetic state at higher temperature to an incommensurate magnetic structure characterized by a magnetic propagation vector (0 0 $\tau )$ with $\tau \approx \frac{1}{4}$ and the magnetic moment along the a axis of the orthorhombic unit cell. Below $T_{\mathrm{LI}}\approx 5$ K, the magnetic structure locks in to a commensurate structure with $\tau =\frac{1}{4}$ and the magnetic moment remains along the a axis. Below $T^{☆}\approx 4$ K, we find additional half-integer and integer indexed magnetic Bragg peaks consistent with a second commensurately ordered antiferromagnetic state.

The thermodynaqmics for intercalation of phenanthrene (PHN) with Ba, for which superconductivity has been reported, is studied in comparison with its isomer of a linear aromatic hydrocarbon of anthracene (AN). Contrary to previous reports by other authors, the important observation that Ba is intercalated into neither PHN nor AN without affecting their molecular structures is unambiguously made by differential scanning calorimetry measurements and annealing time dependences observed by powder x-ray diffraction (XRD) measurements. The reactions of Ba and PHN at elevated temperatures lead this system to molecular decomposition instead of intercalation, resulting in the $\mathrm{Ba}{\mathrm{C}}_2$ carbide or amorphous carbon formation, which is clearly supported by XRD and Raman spectroscopy. The phenomena of metallicity and superconductivity in PHN intercalated with alkaline-earth metals (Ba or Sr) should be reconsidered.

The strongly correlated cuprate ${\mathrm{Cu}}_2{\mathrm{OSeO}}_3$ has been recently identified as the first insulating system exhibiting a skyrmion lattice phase. Using a microscopic multiboson theory for its magnetic ground state and excitations, we establish the presence of two distinct types of modes: a low-energy manifold that includes a gapless Goldstone mode and a set of weakly dispersive high-energy magnons. These spectral features are the most direct signatures of the fact that the essential magnetic building blocks of ${\mathrm{Cu}}_2{\mathrm{OSeO}}_3$ are not individual Cu spins, but rather weakly coupled ${\mathrm{Cu}}_4$ tetrahedra. Several of the calculated excitation energies are in excellent agreement with terahertz electron spin resonance, Raman, and far-infrared experiments, while the magnetoelectric effect determined within the present quantum-mechanical framework is also fully consistent with experiments, giving strong evidence in the entangled ${\mathrm{Cu}}_4$ tetrahedra picture of ${\mathrm{Cu}}_2{\mathrm{OSeO}}_3$. The predicted energy and momentum dependence of the dipole and quadrupole spin structure factors call for further experimental tests of this picture.

Inelastic neutron scattering experiments were performed to study manganese(II) dimer excitations in the diluted one-, two-, and three-dimensional compounds $\mathrm{CsM}{\mathrm{n}}_x\mathrm{M}{\mathrm{g}}_{1-x}\mathrm{B}{\mathrm{r}}_3$, ${\mathrm{K}}_2\mathrm{M}{\mathrm{n}}_x\mathrm{Z}{\mathrm{n}}_{1-x}{\mathrm{F}}_4$, and $\mathrm{KM}{\mathrm{n}}_x\mathrm{Z}{\mathrm{n}}_{1-x}{\mathrm{F}}_3$ ($x\le 0.10$), respectively. The transitions from the ground-state singlet to the excited triplet, split into a doublet and a singlet due to the single-ion anisotropy, exhibit remarkable fine structures. These unusual features are attributed to local structural inhomogeneities induced by the dopant Mn atoms, which act like lattice defects. Statistical models support the theoretically predicted decay of atomic displacements according to $1/r^2$, $1/r$, and constant (for three-, two-, and one-dimensional compounds, respectively) where $r$ denotes the distance of the displaced atoms from the defect. The observed fine structures allow a direct determination of the local exchange interactions $J$, and the local intradimer distances $R$ can be derived through the linear law $dJ/dR$.

We have observed Shubnikov–de Haas oscillations in FeSe. The Fermi surface deviates significantly from predictions of band-structure calculations and most likely consists of one electron and one hole thin cylinder. The carrier density is in the order of 0.01 $\mathrm{carriers}/\mathrm{Fe}$, an order of magnitude smaller than predicted. Effective Fermi energies as small as 3.6 meV are estimated. These findings call for elaborate theoretical investigations incorporating both electronic correlations and orbital ordering.

The hope to realize Majorana fermions at the vortex core of a two-dimensional topological superconductor has led to a variety of proposals for devices which exhibit topological superconductivity. Many of these include superconductivity through the proximity effect and therefore require a layer of a conventional superconductor deposited on top of another system, which lends its topological properties. The necessity of the superconducting layer poses some technical complications and, in particular, makes it harder to probe the Majorana state. In this work we propose to replace the proximity effect pairing by an innate tendency for pairing, mediated by interactions. We use a model system with spin-orbit coupling and on-site repulsion and apply renormalization group to the interaction vertex. Without a Zeeman field this model exhibits pairing instabilities in different channels depending on the tuning of parameters. Once a Zeeman field is introduced the model favors topological superconductivity where the order parameter winds an odd number of times around the Fermi surface. This suggests that certain superconductors, with strong spin-orbit coupling, may go through a topological phase transition as a function of applied magnetic field.

Polaron traps are ubiquitous in organic semiconductors and recent evidence suggests they might be crucial for the large observed magnetic field effects (MFEs) in organic semiconductors. Here we measure MFEs in polymer thin-film devices with engineered, radiative trap sites in order to spectroscopically investigate the influence of the traps. Surprisingly, the luminescence at the trap sites and the polymer backbone is found to have an opposite response to a magnetic field. All our results are compatible with a mechanism in which spin mixing at the traps can create the large MFEs observed on the backbone. This scenario is quantitatively confirmed by numerical drift-diffusion modeling with magnetic-field-dependent exciton densities at the traps. These insights solve an outstanding controversy within the research field.

We study the stability of the corundum, gallia, and bixbyite structures of ${\mathrm{Al}}_2{\mathrm{O}}_3,{\mathrm{Ga}}_2{\mathrm{O}}_3$, and ${\mathrm{In}}_2{\mathrm{O}}_3$ with density functional theory calculations. To artificially control the relative position of the $d$ states within the band structure, we add a Hubbard-like on-site Coulomb interaction to the $d$ states. We quantitatively show that smaller (larger) atomic radii favor the corundum (bixbyte) structure, which supports empirical models based on the atomic radius ratio between the cation and anions and the spacing-filling condition. Thus, ${\mathrm{Al}}_2{\mathrm{O}}_3$ and ${\mathrm{In}}_2{\mathrm{O}}_3$ crystallizes in the corundum and bixbyite structures, which is consistent with experimental observations. The empirical models based on atomic radius and space filling would predict a corundum or bixbyite structure for ${\mathrm{Ga}}_2{\mathrm{O}}_3$. However, as expected from experimental observations, we find gallia to be the most stable structure for ${\mathrm{Ga}}_2{\mathrm{O}}_3$. Our results explain why ${\mathrm{Ga}}_2{\mathrm{O}}_3$ crystallizes in the gallia structures instead of the corundum or bixbyite as follows. The stability of gallia increases as the hybridization of the Ga $d$ states with the O $2s$ states grows and the $p\text{−}d$ splitting increases, which is maximized by the presence of fourfold cation sites. The presence of the fourfold cation sites in gallia is a key structural feature that increases its relative stability compared with the corundum and bixbyite structures for ${\mathrm{Ga}}_2{\mathrm{O}}_3$, which contain only sixfold cation sites, so that the effect of the $d$ states is unimportant.

A combined experimental-theoretical study of optically pumped nuclear magnetic resonance (OPNMR) has been performed in a $\mathrm{GaAs}\text{/}\mathrm{A}{\mathrm{l}}_{0.1}\mathrm{G}{\mathrm{a}}_{0.9}\mathrm{As}$ quantum well film epoxy bonded to a Si substrate with thermally induced biaxial strain. The photon energy dependence of the Ga OPNMR signal was recorded at magnetic fields of 4.9 and 9.4 T at a temperature of 4.8–5.4 K. The data were compared to the nuclear spin polarization calculated from the electronic structure and differential absorption to spin-up and spin-down states of the electron conduction band using a modified $\mathbf{k}·\mathbf{p}$ model based on the Pidgeon-Brown model. Comparison of theory with experiment facilitated the assignment of features in the OPNMR energy dependence to specific interband Landau level transitions. The results provide insight into how effects of strain and quantum confinement are manifested in optical nuclear polarization in semiconductors.

The structural properties of graphene/Ni(111) are investigated by a combination of low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), angle-scanned photoelectron diffraction (PED), and first-principles calculations. XPS data indicate that graphene interacts strongly with the topmost Ni layer. Diffraction data show that graphene is deposited commensurably with the underlying Ni surface atoms. Twelve different graphene preparations were analyzed by LEED and one by PED. Considering the relative position between the carbon and Ni atoms, five experimental sets indicate a top-fcc structure, three show a bridge-top structure, and four have a mixed structure. The analysis of the PED experiment suggests the top-fcc termination. Our first-principles calculations show that the total energies of the top-fcc and bridge-top structures are nearly degenerate, which corroborates the observed bistability of those phases. Moreover, by comparing the structural parameters obtained by the three methods (LEED, PED, and ab initio calculations), excellent agreement is achieved.

The Tl/Si(111)-$\left(1\times 1\right)$ surface features outstanding properties with a unique spin pattern in momentum space. Along $\overline{\Gamma }\overline{K}$ $\left(\overline{\Gamma }{\overline{K}}^{\prime }\right)$, surface states with rotating spin had been observed. Here, the focus is put on the unoccupied surface electronic structure along the $\overline{\Gamma }\overline{M}$ high-symmetry direction. Spin- and angle-resolved inverse-photoemission experiments with sensitivity to the in-plane and out-of-plane components of the spin-polarization vector are conducted with the help of our recently developed rotatable spin-polarized electron source (ROSE). In agreement with our theoretical findings, we identify a surface resonance with giant spin-orbit-induced spin splitting, which exhibits an exclusive Rashba-type spin texture, i.e., a pure in-plane spin polarization perpendicular to $\overline{\Gamma }\overline{M}$, in compliance with the mirror-plane symmetry of the $\overline{\Gamma }\overline{M}$ direction. Notably, for slight deviations from the high-symmetry line, this constraint is lifted and additional spin-polarization components emerge. This highlights the importance of a correct alignment of the experiment when investigating samples with spin textures that are more complex than in simple Rashba systems or in ferromagnets.

We synthesize and study single crystals of the layered honeycomb lattice Mott insulators ${\mathrm{Na}}_2{\mathrm{RuO}}_3$ and ${\mathrm{Li}}_2{\mathrm{RuO}}_3$ with magnetic ${\mathrm{Ru}}^{4+}\left(4d^4\right)$ ions. The newly found ${\mathrm{Na}}_2{\mathrm{RuO}}_3$ features a nearly ideal honeycomb lattice and orders antiferromagnetically at 30 K. Single crystals of ${\mathrm{Li}}_2{\mathrm{RuO}}_3$ adopt a honeycomb lattice with either $C2/m$ or more distorted $P{2}_1/m$ below 300 K, depending on detailed synthesis conditions. We find that ${\mathrm{Li}}_2{\mathrm{RuO}}_3$ in both structures hosts a well-defined magnetic state, in contrast to the singlet ground state found in polycrystalline ${\mathrm{Li}}_2{\mathrm{RuO}}_3$. A phase diagram generated based on our results uncovers a new, direct correlation between the magnetic ground state and basal-plane distortions in the honeycomb ruthenates.

Using ab initio calculations we predict the existence of one-dimensional (1D), atomically confined plasmons at the edges of a zigzag ${\mathrm{MoS}}_2$ nanoribbon. The strongest plasmon originates from a metallic edge state localized on the sulfur dimers decorating the Mo edge of the ribbon. A detailed analysis of the dielectric function reveals that the observed deviations from the ideal 1D plasmon behavior result from single-particle transitions between the metallic edge state and the valence and conduction bands of the ${\mathrm{MoS}}_2$ sheet. The Mo and S edges of the ribbon are clearly distinguishable in calculated spatially resolved electron energy loss spectrum owing to the different plasmonic properties of the two edges. The edge plasmons could potentially be utilized for tuning the photocatalytic activity of ${\mathrm{MoS}}_2$ nanoparticles.