Zel'dovich (spin) anapole correlations in $\mathrm{S}{\mathrm{r}}_2\mathrm{Ir}{\mathrm{O}}_4$ unveiled by magnetic neutron diffraction contravene the spin-orbit coupled ground state used by the $j_{\mathrm{eff}}=1/2$ (pseudospin) model. Specifically, spin and space know inextricable knots which bind each to the other in the iridate. The diffraction property studied in the paper is enforced by strict requirements from quantum mechanics and magnetic symmetry. It has not been exploited in the past, whereas neutron diffraction by anapole moments is established. Entanglement of the electronic degrees of freedom is captured by dyadic correlations of the anapole and position operators, and hallmarked in the diffraction amplitude by axial atomic multipoles with an even rank.

Shock waves are a ubiquitous feature of hydrodynamic theories. Given that fermionic quantum many-body systems admit hydrodynamical descriptions on length scales large compared to the Fermi wavelength, it is natural to ask what the status of shock waves is in such systems. Free fermions provide a solvable yet nontrivial example, and here we generalize to include generic (nonintegrable) weak interactions to understand how a shock wave decays and changes its shape well after forming.

Magnetotransmission (MT) at magnetic fields up to 29 T was used to study the electronic structure of $\mathrm{CuInS}{\mathrm{e}}_2$ in thin polycrystalline films. The zero field absorption spectra exhibited resolved A, B, and C free excitons. Quantum oscillations, due to diamagnetic excitons comprising electrons and holes from Landau levels quantized in the conduction and valence band, respectively, appeared in the MT spectra at fields over 5 T. Spectral energies of Landau levels and binding energies of the corresponding diamagnetic excitons, theoretically calculated assuming a quasicubic approximation of the $\mathrm{CuInS}{\mathrm{e}}_2$ tetragonal lattice structure, helped to identify the character of the experimentally observed diamagnetic excitons. Spectral energies of diamagnetic excitons in the MT spectra with different circular polarizations were used to determine the electron and light hole effective masses, whereas heavy hole masses as well as the γ and ${\gamma }_1$ Luttinger parameters, $E_p$ Kane energy, and F parameter of the influence of remote bands, as well as their polaron values, were calculated using the Luttinger theory.

Many molecular junctions display stochastic telegraphic switching between two distinct current values, which is an important source of fluctuations in nanoscale quantum transport. Using Markovian master equations, we investigate electronic fluctuations and identify regions of nonrenewal behavior arising from telegraphic switching. Nonrenewal behavior is characterized by the emergence of correlations between successive first-passage times of detection in one of the leads. Our method of including telegraphic switching is general for any source-molecule-drain setup, but we consider three specific cases. In the first, we model stochastic transitions between an Anderson impurity with and without an applied magnetic field $B$. The other two scenarios couple the electronic level to a single vibrational mode via the Holstein model. We then stochastically switch between two vibrational conformations, with different electron-phonon coupling $\lambda$ and vibrational frequency $\omega$, which corresponds to different molecular conformations. Finally, we model the molecule attaching and detaching from an electrode by switching between two different molecule-electrode coupling strengths $\gamma$. We find, for all three cases, that including the telegraph process in the master equation induces relatively strong positive correlations between successive first-passage times, with Pearson coefficient $p\approx 0.5$. These correlations only appear, however, when there is telegraphic switching between two significantly different transport scenarios, and we show that it arises from the underlying physics of the model. We also find that, in order for correlations to appear, the switching rate $\nu$ must be much smaller than $\gamma$.

We consider an impurity in a semi-infinite one-dimensional system of weakly-interacting bosons. We calculate the interaction potential for the impurity due to the end of the system, i.e., the wall. For local repulsive (attractive) interaction between the impurity and the Bose gas, the interaction potential is attractive (repulsive). At short distances from the wall it decays exponentially crossing over into a universal $1/r^2$ behavior at separations $r$ above the healing length. Our results can also be interpreted as a Casimir-like interaction between two impurities, where one of them is infinitely strongly coupled to the Bose gas. We discuss various scenarios for the induced interaction between the impurities using the scattering approach. We finally address the phenomenon of localization of the impurity near the wall. In the paper we mainly study the case of a static impurity, however the universal $1/r^2$ interaction also holds for a slowly moving impurity.

The generation of spin current is of significant importance for advanced spintronic applications. In conventional theory and experiment, microwave sources are usually described by a classical time-varying field in which all fluctuations are neglected. Here, we study the spin current driven by nonclassical light by developing a Green's function method in which both effects of nonclassical light and electron-related interaction can be taken into account. Our theoretical method has more advantages than the linear response theory developed recently as it can be easily extended to the electronic transport problem with interaction. As an example, we calculate the spin current due to the rotating magnetic field in the presence of nonclassical light. It is found that the spin current is sensitive to the state of nonclassical light. Under certain conditions, the transmission and spin current can be smaller than the classical limit, which cannot be broken by a pure classical microwave field. The method developed here and the results reported here will be important for understanding complicated physical phenomena occurring in the hybrid field of spintronics and circuit quantum electrodynamics.

A model demonstrating the existence of a thermodynamically stable quantum time-space crystal has been proposed and studied. This state is characterized by an order parameter periodic in both real and imaginary times. The average of the order parameter over phases of the oscillations vanishes but correlation functions of two or more order parameters show nondecaying oscillations. An alternative interpretation of the results is based on the concept of an operator order parameter introduced for this purpose. The model studied here has been suggested previously, in particular, for describing the pseudogap state in superconducting cuprates. Although many properties of the time-space crystal considered here are close to those of a well known DDW state, static magnetic moments oscillating at $(\pi ,\pi )$ do not exist. Instead, $\delta$ peaks at finite energies are predicted in the cross-section of inelastic spin-polarized neutron scattering.

We investigate numerically the problem of few (one or two) noninteracting spin-$1/2$ fermions in a shallow harmonic trap coupled via contact repulsive interactions to a uniform one-dimensional bath of lattice bosons, described by the Bose-Hubbard model. Through extensive density-matrix renormalization group calculations, we extract the binding energy and the effective mass of quasiparticles, including dressed impurities (polarons) and their two-body bound states (bipolarons), emerging from the effective nonlocal Casimir interaction between the impurities. We show that the mixture exhibits rather different pairing behaviors depending on the singlet vs triplet spin state configurations of the two fermions. For opposite spin states, bipolarons are found for any finite value of the impurity-bath coupling. In particular, in the strong-coupling regime their binding energy reduces to that of a single polaron, provided the boson-boson repulsion is not too weak. For equal spin states, we show that bipolarons emerge only beyond a critical strength of the Bose-Fermi interaction and their effective mass grows rapidly approaching the strong-coupling regime.

Two-dimensional-layered tin (II) oxide (SnO) has recently emerged as a promising bipolar channel material for thin-film transistors and complementary metal-oxide-semiconductor devices. In this paper, we present a first-principles investigation of the mechanical properties of ultrathin SnO as well as the electronic implications of tensile strain ($\epsilon$) under both uniaxial and biaxial conditions. Bulk-to-monolayer transition is found to significantly lower the Young's and shear moduli of SnO, highlighting the importance of interlayer Sn-Sn bonds in preserving structural integrity. Unprecedentedly, few-layer SnO exhibits superplasticity under uniaxial deformation conditions with a critical strain to failure of up to 74% in the monolayer. Such superplastic behavior is ascribed to the formation of a tricoordinated intermediate (referred to here as $h$-SnO) beyond $\epsilon =14\%$, which resembles a partially-recovered orthorhombic phase with a relatively large work function and wide indirect band gap. The broad structural range of tin (II) oxide under strongly anisotropic mechanical loading suggests intriguing possibilities for realizing novel hybrid nanostructures of SnO through strain engineering. The findings reported in this study reveal fundamental insights into the mechanical behavior and strain-driven electronic properties of tin (II) oxide, opening up exciting avenues for the development of SnO-based nanoelectronic devices with new, nonconventional functionalities.

The macroscopic resistivity tensor of a two-constituent flat-slab composite structure subject to an external magnetic field B is found by exact evaluation of the local electric field and current density. Despite the seemingly simple route to this exact calculation, some of the results are surprising. In particular, circumstances are found under which the macroscopic Ohmic resistivities keep increasing with B without any saturation, even when the constituent Ohmic resistivities have saturated. We also present an approximate treatment of the macroscopic resistivity tensor for an isotropic microstructure.

SnS and SnSe are isoelectronic materials with a common phase diagram. Recently, SnSe was found to be the most efficient intrinsic thermoelectric material in its high-temperature $Cmcm$ phase above 800 K. Making use of first-principles calculations, here we show that the electronic and vibrational properties of both materials are very similar in this phase and, consequently, SnS is also expected to have a high thermoelectric figure of merit at high temperature in its $Cmcm$ phase. In fact, the electronic power factor and lattice thermal conductivity are comparable for both materials, which ensures a similar figure of merit. As in the case of SnSe, the vibrational properties of SnS in the $Cmcm$ phase are far from trivial and are dominated by huge anharmonic effects. Its phonon spectra are strongly renormalized by anharmonicity and the spectral functions of some particular in-plane modes depict anomalous non-Lorentzian profiles. Finally, we show that nonperturbative anharmonic effects in the third-order force-constants are crucial in the calculation of the lattice thermal conductivity. Our results motivate new experiments in the high-temperature regime to measure the figure of merit of SnS.

The classical Doppler shift originates from the movement of a target's center of mass, but it does not hold information about the internal dynamics of the scattering object. In contrast, micro-Doppler signatures contain data about the micromotions that arise from internal degrees of freedom within the target (such as rotation and vibration), which can be remotely detected by careful analysis of the scattered field. Here we investigate, both theoretically and experimentally, how coupling between a pair of closely situated targets affects the resulting micro-Doppler signatures. The presented model considers a pair of near-field coupled resonators with dynamically reconfigurable scattering properties. Voltage controlled varactor diodes enable modulating the scattering cross section of each target independently, mimicking rotational degrees of freedom. As a result, coupled micro-Doppler combs are observed, containing frequency components that arise from the near field interactions, making it possible to extract information about the internal geometry of the system from far-field measurements. From a practical point of view, micro-Doppler spectroscopy allows remote classification of distant objects, while deep understanding of the coupling effects on such signatures in the low frequency regime can provide valuable insight for radar and sonar systems, as well as optical and stellar radio-interferometry, among many others.

We study the anomalous Hall effect at a ${\mathrm{PtO}}_x/\mathrm{Co}$ interface. We extracted the intrinsic and extrinsic contributions to the anomalous Hall effect in ${\mathrm{SiO}}_2/\mathrm{Co}/{\mathrm{SiO}}_2$ and ${\mathrm{PtO}}_x/\mathrm{Co}/{\mathrm{SiO}}_2$ films by measuring temperature dependence of the anomalous Hall resistivity. The result shows that the intrinsic anomalous Hall effect in the ${\mathrm{PtO}}_x/\mathrm{Co}/{\mathrm{SiO}}_2$ film is almost identical to that in the ${\mathrm{SiO}}_2/\mathrm{Co}/{\mathrm{SiO}}_2$ film. In contrast, the extrinsic anomalous Hall effect is clearly different between the ${\mathrm{SiO}}_2/\mathrm{Co}/{\mathrm{SiO}}_2$ and ${\mathrm{PtO}}_x/\mathrm{Co}/{\mathrm{SiO}}_2$ films. The anomalous Hall effect for various Co-layer thicknesses $t$ at various temperatures reveals that the extrinsic anomalous Hall resistivity shows a $t^{-1}$ dependence in the ${\mathrm{PtO}}_x/\mathrm{Co}/{\mathrm{SiO}}_2$ film, while it is almost independent of $t$ in the ${\mathrm{SiO}}_2/\mathrm{Co}/{\mathrm{SiO}}_2$ film. This result demonstrates the extrinsic anomalous Hall effect originating from the ${\mathrm{PtO}}_x/\mathrm{Co}$ interface. Our results show that both the side-jump and skew-scattering mechanisms contribute to the interfacial anomalous Hall effect, which can be attributed to the formation of Co-O bonds and electron scattering by Pt impurities at the ${\mathrm{PtO}}_x/\mathrm{Co}$ interface.

The self-energy Padé approach is discussed as an analytic continuation of numerical methods that evaluate correlation functions in imaginary time. Instead of direct analytic continuation of the correlation functions, the Padé method is applied for the self-energy in this approach, which is then used for deriving the Green's functions at real energies. We demonstrate that the self-energy Padé approach is more stable and robust against statistical errors compared to the direct way. The characteristics and success of the self-energy Padé approach are analyzed by actual calculations for the illustrative examples of the noninteracting Anderson lattice and interacting Hubbard model. A zero-gap Kondo lattice model with linearly vanishing conduction electron density of states at the Fermi level is also studied by using the self-energy Padé approach as an analytic continuation. We investigate the properties of the Kondo insulating state including the dependence of the insulating gap on the Kondo coupling and coherence effects. Furthermore, we identify two energy scales from dynamic and thermodynamic quantities that are associated as a direct and an indirect gap in a band hybridization picture.

The critical behavior of Heusler alloy $\mathrm{Co}{}_2\mathrm{TiSn}$ is investigated by bulk magnetization study around the paramagnetic to ferromagnetic transition. The precise value of Curie temperature ($T{}_c=358\mathrm{K}$) as well as the critical exponents ($\beta =0.527\pm 0.003, \gamma =1.229\pm 0.002$, and $\delta =3.33\pm 0.002$) were determined by means of different analytical methods such as modified Arrott plot analysis, the Kouvel-Fisher method, and critical isotherm analysis. With these critical exponents the isotherm $M\left(H\right)$ curves below and above $T{}_c$ collapse into two universal branches, fulfilling the single scaling equation $m=f_{\pm }h$, where $m$ and $h$ are normalized magnetization and field, respectively. The reliability of the critical exponents were confirmed by Widom scaling hypothesis $\delta =\gamma {\beta }^{-1}$. Apart from the slight increase in $\beta$ and $\gamma$, the deduced critical exponents were consistent with the theoretical prediction of the mean-field model, indicating the long range magnetic interaction in $\mathrm{Co}{}_2\mathrm{TiSn}$. Additionally, it is obtained that spin interaction decays as $J\left(r\right)\sim r^{-4.7}$. We suggest that the competition between localized majority spins and itinerant minority spins magnetic interaction could be responsible for critical behavior in $\mathrm{Co}{}_2\mathrm{TiSn}$.

The possible superconducting states of strontium ruthenate $\left({\mathrm{Sr}}_2{\mathrm{RuO}}_4\right)$ are organized into irreducible representations of the point group $D_{4h}$, with a special emphasis on nodes occurring within the superconducting gap. Our analysis covers the cases with and without spin-orbit coupling and takes into account the possibility of interorbital pairing within a three-band, tight-binding description of ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$. No dynamical treatment if performed: We are confining ourselves to a group-theoretical analysis. We nevertheless adopt an intermediate-coupling point of view by working in the orbital basis instead of the band basis. The case of uniaxial deformations, under which the point group symmetry is reduced to $D_{2h}$, is also covered. It turns out that nodal lines, in particular equatorial nodal lines, occur in most representations. We also highlight some results specific to multiorbital superconductivity. Among other things, we find that odd interorbital pairing allows us to combine singlet and triplet superconductivity within the same irreducible representation, that pure interorbital superconductivity leads to nodal surfaces and that the notion of nodes imposed by symmetry is not clearly defined.

We performed quartz crystal microbalance experiments for a ${}^3\mathrm{He}\text{−}{}^4\mathrm{He}$ mixture film on an exfoliated single-crystalline graphite using a 32-kHz quartz tuning fork. The decoupled ${}^3\mathrm{He}$ overlayer on the superfluid ${}^4\mathrm{He}$ layer shows a reentrant pinning at a certain temperature $T_{3d}$ under a large oscillation amplitude. The pinning state below $T_{3d}$ is metastable. After reducing the oscillation amplitude, the ${}^3\mathrm{He}$ overlayer relaxes to a stable pinning state via a depinning state. It is found that the reentrant pinning is triggered by a structure change of the underlying localized ${}^4\mathrm{He}$ layer on the oscillating substrate.

Two-dimensional triangular-lattice materials with spin-1/2 are perfect platforms for investigating quantum frustrated physics with spin fluctuations. Here we report the structure, magnetization, heat capacity, and inelastic neutron scattering (INS) results on cesium ytterbium diselenide, ${\mathrm{CsYbSe}}_2$. There is no long-range magnetic order down to 0.4 K at zero field. The temperature-dependent magnetization, $M\left(T\right)$, reveals an easy-plane magnetic anisotropy. A maximum is found in $M\left(T\right)$ around $T\approx 1.5$ K when magnetic field $H$ is applied in the $ab$ plane, indicating the short-range interaction. The low-temperature isothermal magnetization $M\left(H\right)$ shows a one-third plateau of the estimated saturation moment, which is characteristic of a two-dimensional (2D) frustrated triangular lattice. Heat capacity shows field-induced long-range magnetic order for both $H\left|\right|c$ and $H\left|\right|ab$ directions. The broad peak in heat capacity and highly damped INS magnetic excitation at $T=2$ K suggests strong spin fluctuations. The dispersive in-plane INS, centered at the (1/3 1/3 0) point, and the absence of dispersion along the $c$ direction suggest ${120}^{\circ }$ noncollinear 2D-like spin correlations. All these results indicate that the two-dimensional frustrated material ${\mathrm{CsYbSe}}_2$ can be in proximity to the triangular-lattice quantum spin liquid. We propose an experimental low-temperature $H\text{−}T$ phase diagram for ${\mathrm{CsYbSe}}_2$.

Magnetic proximity effect has only been conclusively observed in ferromagnet-based systems. We report the observation of anomalous Hall effect and angular-dependent anisotropic magnetoresistance in Pt on antiferromagnetic $\alpha \text{−}\mathrm{F}{\mathrm{e}}_2{\mathrm{O}}_3\left(0001\right)$ epitaxial films at 10 K, which provide evidence for the magnetic proximity effect. The Néel order of $\alpha \text{−}\mathrm{F}{\mathrm{e}}_2{\mathrm{O}}_3$ and the induced magnetization in Pt show a unique angular-dependent magnetoresistance compared with all other ferromagnetic and antiferromagnetic systems. A macrospin response model is established and can explain the antiferromagnetic spin configuration and all main magnetoresistance features in the $\mathrm{Pt}/\alpha \text{−}\mathrm{F}{\mathrm{e}}_2{\mathrm{O}}_3$ bilayers.