The mechanism of Kondo screening in strongly correlated molecules with several unpaired electrons on a metal surface is still under debate. Here, we provide a theoretical framework that rationalizes the emergence of Kondo screening involving several extended molecular orbitals with unpaired electrons. We introduce a perturbative model, which provides simple rules to identify the presence of antiferromagnetic spin-flip channels involving charged molecular multiplets responsible for Kondo screening. The Kondo regime is confirmed by numerical renormalization group calculations. In addition, we introduce the concept of Kondo orbitals as molecular orbitals associated with the Kondo screening process, which provide a direct interpretation of experimental $\mathrm{d}I/\mathrm{d}V$ maps of Kondo resonances. We demonstrate that this theoretical framework can be applied to different strongly correlated open-shell molecules on metal surfaces, obtaining good agreement with previously published experimental data.

Earlier theoretical results on $p\text{−}d$ and $d\text{−}d$ exchange interactions for zinc-blende semiconductors with ${\mathrm{Cr}}^{2+}$ and ${\mathrm{Mn}}^{3+}$ ions are revisited and extended by including contributions beyond the dominating ferromagnetic (FM) superexchange term [i.e., the interband Bloembergen-Rowland-Van Vleck contribution and antiferromagnetic (AFM) two-electron term], and applied to topological Cr-doped HgTe and nontopological (Zn,Cr)Te and (Ga,Mn)N in zinc-blende and wurtzite crystallographic structures. From the obtained values of the $d\text{−}d$ exchange integrals $J_{ij}$, and by combining the Monte Carlo simulations with the percolation theory for randomly distributed magnetic ions, we determine magnitudes of Curie temperatures $T_{\text{C}}\left(x\right)$ for ${\mathrm{Zn}}_{1-x}{\mathrm{Cr}}_x\mathrm{Te}$ and ${\mathrm{Ga}}_{1-x}{\mathrm{Mn}}_x\mathrm{N}$ and compare to available experimental data. Furthermore, we find that competition between FM and AFM $d\text{−}d$ interactions can lead to a spin-glass phase in the case of ${\mathrm{Hg}}_{1-x}{\mathrm{Cr}}_x\mathrm{Te}$. This competition, along with a relatively large magnitude of the AF $p\text{−}d$ exchange energy $N_0\beta$ can stabilize the quantum spin Hall effect, but may require the application of tilted magnetic field to observe the quantum anomalous Hall effect in HgTe quantum wells doped with Cr, as confirmed by the Chern number determination.

We focus on the transmission and reflection coefficients of light in systems involving topological insulators (TIs). Due to the electromagnetic coupling in TIs, new mixing coefficients emerge, leading to new components of the electromagnetic fields of propagating waves. We have discovered a simple heterostructure that provides a 100-fold enhancement of the mixing coefficients for TI materials. Such effect depends on the TI's wave impedance and the selected material for the sublayer. We also predict a transverse deviation of the Poynting vector due to these mixed coefficients contributing to the radiative electromagnetic field of an electric dipole. Given an optimal configuration of the dipole-TI system, this deviation could amount to $0.28\%$ of the Poynting vector due to emission near nontopological materials, making this effect detectable.

We demonstrate a toroidal classification for quantum spin systems, revealing an intrinsic geometric duality within this structure. Through our classification and duality, we reveal that various bipartite quantum features in magnon systems can manifest equivalently in both bipartite ferromagnetic and antiferromagnetic materials, based upon the availability of relevant Hamiltonian parameters. Additionally, the results highlight the antiferromagnetic regime as an ultrafast dual counterpart to the ferromagnetic regime, both exhibiting identical capabilities for quantum spintronics and technological applications. Concrete illustrations are provided, demonstrating how splitting and squeezing types of two-mode magnon quantum correlations can be realized across ferro- and antiferromagnetic regimes.

In disordered media, an interference effect called coherent backscattering (CBS) arises from the reciprocity of multiple scattering. When illuminating a medium in a given direction and measuring the intensity of scattered waves, one may observe an amplification around the backward direction. The angular extent of this amplification effect relates to the medium transport properties, which makes it an attractive tool for the characterization of heterogeneous media. However, exploiting this angular extent is challenging in practice because it is often too small to be reliably measured. Fortunately, the amplification of the backscattered intensity is not the only property of the CBS effect. Indeed, we observe an additional phase coherence between waves backscattered in different directions. As such, if the experimental configuration enables the complete measurement of backscattered waves, i.e., amplitude and phase, this phase coherence can be leveraged to enhance the CBS effect by a factor of 2 in both width and amplitude. This enhancement is key for more reliable measurements of transport properties and paves the way to the characterization of disordered media in challenging environments like biological tissues in vivo. In this work, we demonstrate the enhanced CBS effect theoretically and observe it experimentally with ultrasound waves.

We explicitly construct unique nonequilibrium steady state (NESS) of the Lindblad master equation characterized by a Gibbs ensemble ${\rho }_{\text{NESS}}\propto e^{-\beta \tilde{H}}$, where the effective Hamiltonian $\tilde{H}$ consists only of $\text{U}\left(1\right)$ conserved charges of the original Hamiltonian. Specifically, when the original Hamiltonian has multiple charges, it is possible to couple them with bathes at different temperature, respectively, but still leads to an equilibrium state. To access the Gibbs NESS, the jump operators need to be properly chosen to fulfill quantum detailed balance condition (qDBC). These jump operators are ladder operators for $\tilde{H}$ and jump process they generate form a vertex-weighted directed acyclic graph (wDAG). By studying the $XX$ model and Fredkin model, we showcase how the Gibbs state emerges as an equilibrium steady state.

A thermodynamic theory based on Landau grand potential expansion for ferromagnetic-paramagnetic phase transitions is developed for an electronic phase-separated state. It is rigorously shown that ferromagnetic phase involved in the phase-separated state exhibits negative magnetic susceptibility in the vicinity of tricritical point. Thus, an entropy of the magnetically ordered phase may increase when the magnetic field is applied, which implies positive sign of the total magnetic entropy change $\mathrm{\Delta }S$ within magnetocaloric effect (MCE). The electronic phase separation and MCE are considered within the Hubbard model for face-centered cubic lattice with giant van Hove singularity of electron density of states at the band bottom. Within the Hartree-Fock approximation it is shown that such model of itinerant magnet exhibits the first-order ferromagnet-paramagnet phase transition with electronic phase separation and inverse magnetocaloric effect deep inside the phase-separated region. Temperature dependence of $\mathrm{\Delta }S$ for the mean-field solution of the nondegenerate Hubbard model is analyzed in detail for different band filling values. The possibility to control $\mathrm{\Delta }S$ sign by changing both temperature and band filling of magnetocaloric materials is demonstrated. This is important to interpret a lot of experimental data, possible technological applications, and further theoretical developments.

Mesonic bound states of domain walls (DWs) can be stabilized in quasi-one-dimensional magnetic compounds. Here, we theoretically study the Raman light scattering response of a twisted Kitaev chain with tilted magnetic fields as a minimal model for confinement in ${\mathrm{CoNb}}_2{\mathrm{O}}_6$. By both numerical matrix product states and few-DW variational states, we show that confinement-induced bound states directly manifest themselves as sharp peaks in the Raman response. Remarkably, by tuning the polarization of the incident light field, we demonstrate that the Raman response offers insights into the intrinsic symmetry of the bound-state wave function.

The linewidth of antiferromagnetic resonance (AFMR) is notably broader than that of ferromagnetic resonance (FMR), even when both systems share the same intrinsic Gilbert damping parameter. We found that this phenomenon is primarily attributed to an additional phase delay in the two magnetic sublattices of antiferromagnets caused by Gilbert damping. This phase delay introduces a dampinglike component to the originally dissipationless exchange torque, thereby enhancing the damping and broadening the linewidth. Additionally, two alternative explanations are presented: The transverse component of the exchange coupling decreases the AFMR frequency, thus increasing the damping rate, and the antiferromagnetic eigenmode demonstrates properties of a two-mode squeezed state, intrinsically linked to enhanced damping. These findings introduce a different AFM eigenstate under Gilbert damping, impacting magnetic dissipation in antiferromagnets and providing insights into the experimentally observed broadened AFMR linewidths.

Unstable periodic orbits (UPOs) play a key role in the theory of chaos, constituting the “skeleton” of classical chaotic systems and “scarring” the eigenstates of the corresponding quantum system. Recently, nonthermal many-body eigenstates embedded in an otherwise thermal spectrum have been identified as a many-body generalization of quantum scars. The latter, however, are not clearly associated to a chaotic phase space, and the connection between the single- and many-body notions of quantum scars remains therefore incomplete. Here, we find the first quantum many-body scars originating from UPOs of a chaotic phase space. Remarkably, these states verify the eigenstate thermalization hypothesis, and we thus refer to them as thermal quantum many-body scars. While they do not preclude thermalization, their spectral structure featuring approximately equispaced towers of states yields an anomalous oscillatory dynamics preceding thermalization for wavepackets initialized on an UPO. Remarkably, our model hosts both types of scars, thermal and nonthermal, and allows us to study the crossover between the two. Our work illustrates the fundamental principle of classical-quantum correspondence in a many-body system and its limitations.

${\mathrm{Gd}}_4{\mathrm{Sb}}_3$ is a typical of half-metallic ferromagnet possessing six-, four-, and threefold band crossings, in which also exists a distinct energy gap in the minority spin projection, but quite high density of states for the majority spin projection around the Fermi energy. Such a band structure makes ${\mathrm{Gd}}_4{\mathrm{Sb}}_3$ an excellent platform in studying the anomalous magnetic and electrical transport properties. In this study, the ${\mathrm{Gd}}_4{\mathrm{Sb}}_3$ polycrystalline sample was synthesized and the anomalous Hall and Nernst responses were investigated by means of comprehensive electrical, thermal, and thermoelectric measurements and the first-principles calculation. It is worth noting that a large intrinsic anomalous Hall conductivity distribution (AHC, ${\sigma }_{xy}^{\mathrm{int}}\sim 233{\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$) and anomalous transverse thermoelectric conductivity (ANC, ${\alpha }_{yx}^{\mathrm{A}}$ $\sim 0.84\mathrm{A}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$) are extracted. Our first-principles calculations reveal a large Berry curvature near the Fermi level, which gives the physical origin of large AHC and ANC values. This work may pave an avenue to search for new materials with large AHE and ANE from the half-metallic ferromagnets with topological nontrivial electronic band structures.

We discuss the instability of uniform superconducting states in $j=3/2$ superconductors that contain the pairing correlations belonging to the odd-frequency symmetry class. The instability originates from the paramagnetic response of odd-frequency Cooper pairs and is considerable at finite temperatures. As a result, the pair potential varies discontinuously at the transition temperature when the amplitude of the odd-frequency pairing correlation functions is sufficiently large. We also discuss the discontinuous transition in other uniform superconductors.

${\mathrm{LaRu}}_2{\mathrm{P}}_2$ shares a similar ${\mathrm{ThCr}}_2{\mathrm{Si}}_2$-type structure with iron pnictides and also shows a superconductivity of $\sim 4$ K, but possesses quite different electronic properties. The studies of electronic properties and superconductivity in ${\mathrm{LaRu}}_2{\mathrm{P}}_2$ are of particular interest. In this paper, we have conducted a comprehensive Raman scattering study and careful first-principles calculations to explore the electron-phonon coupling (EPC) in ${\mathrm{LaRu}}_2{\mathrm{P}}_2$. We have grown very high-quality ${\mathrm{LaRu}}_2{\mathrm{P}}_2$ superconducting single crystals with a superconducting transition width $\mathrm{\Delta }{T}_c\sim 0.15$ K. The phonon modes observed in polarized Raman measurements are well assigned with a symmetry analysis. The linewidths of the Raman modes exhibit an anomalous temperature dependence though their Raman frequencies approximately follow the general anharmonic decay process. This allows us to extract the intrinsic phonon broadening caused by EPC, and gives a relatively large EPC constant which is consistent with our first-principles calculations. The estimated $T_c\sim 4.2$ K based on the constant suggests a pairing mechanism associated with EPC in ${\mathrm{LaRu}}_2{\mathrm{P}}_2$.

Controlling many-body quantum systems is a highly challenging task required to advance quantum technologies. Here, we report progress in controlling gapless many-body quantum systems described by the Tomonaga-Luttinger liquid (TLL). To do so, we investigate the exact dynamics of the TLL induced by an arbitrary interaction quench, making use of the $\text{SU}(1,1)$ dynamical symmetry group and the Schrödinger picture. First, we demonstrate that this approach is useful to perform a shortcut to adiabaticity, which cancels the final nonadiabatic residual energy of the driven TLL and is experimentally implementable in the semiclassical limit of the sine-Gordon model. Second, we apply this framework to analyze various driving schemes in finite time, including linear ramps and smooth protocols.

Through quasiparticle self-consistent $GW$, we investigate the electronic structure of the antiferromagnetic ground state of four transition-metal monoxides: MnO, FeO, CoO, and NiO. In addition to the random-phase approximation, we consider two different schemes incorporating effective vertex corrections. The first scheme includes in the polarizability a vertex function derived from the solution of the Bethe-Salpeter equation (BSE), whereas the second scheme includes in both the polarizability and self-energy a vertex function, which carries a long-range part satisfying the Ward identity and a short-range part derived from the adiabatic local density approximation. Our results include fundamental band gaps, macroscopic dielectric constants, and local magnetic moments, emphasizing the role of vertex corrections in the description of these key electronic properties. We provide quasiparticle band structures and projected densities of states allowing us to establish a connection with the Mott insulator picture and to highlight the overall good agreement with experimental photoemission spectra. The inclusion of the vertex in the self-energy preserves the overall shape of the band structures but generally produces larger rigid energy shifts for $d$ bands than for $sp$ bands. Through the solution of the Bethe-Salpeter equation, we determine excitonic effects and obtain dielectric response functions. Despite the experimental uncertainties, which appear sizable in the case of FeO, it is possible to discern a good general correspondence between the calculated and measured spectra, particularly for the absorption onsets and the peak positions. Furthermore, deep excitons are found to occur in the absorption spectra of FeO, CoO, and NiO, in qualitative agreement with the available characterization. Our work indicates that many-body perturbation theory including effective vertex corrections is able to provide a quantitatively accurate description of key electronic-structure features of transition-metal monoxides.

The nonreciprocity of critical supercurrents in a Josephson device, termed the Josephson diode effect (JDE), has drawn considerable interest recently. Herein, we present possible spin-resolved and charge JDEs in a Josephson junction based on the $\alpha \text{−}{T}_3$ lattice, due to different spin-resolved Fermi velocities in opposite directions for the distorted flat bands and edge states. Two mechanisms are exhibited, which are characterized by a topological phase with an anisotropic parameter $\alpha$. One is that the JDE only originates from distorted flat bands, corresponding to the topological phase $(0<\alpha <0.5)$, the other simultaneously from edge states in the topological phase $(0.5<\alpha <1)$. Particularly, the charge JDE only manifests in the context of magnetization and its efficiency can range from $-45\%$ to $39\%$, suggesting a high nonreciprocity. More importantly, both the magnitude and polarity of the charge JDE from edge states and distorted flat bands can be strongly adjusted by the magnetization strength.

We study transmission of the terahertz radiation through a two-dimensional electron gas with a concentration controlled by grating gate electrodes. Voltage applied to these electrodes creates a lateral plasmonic crystal with a gate-tunable band structure. We find that only a part of plasmonic modes of such a crystal is seen in the transmission spectrum for the case of homogeneous excitation (so-called bright modes), while there also exist dark modes which show up only in a case of inhomogeneous excitation. We develop a theory that describes both weak-to-strong coupling transition in the crystal with increasing depth of the density modulation and a transition from resonant to super-resonant regime with increasing quality factor of the structure. We discuss very recent experiments, where transmission of the terahertz radiation through GaN/AlGaN-based grating-gate periodic structures was studied. We argue that this experiment represents an evidence of formation of the lateral plasmonic crystal with the band structure fully controlled by the gate electrodes, in a full agreement with developed theory.

Intercalation of magnetic atoms into the van der Waals gaps of layered transition metal dichalcogenides offers an excellent platform to produce exotic physical properties. Here, we report a detailed study of magnetic and electrical transport properties of ${\mathrm{Co}}_{0.28}{\mathrm{TaS}}_2$. The temperature-dependent resistivity measurements display an anomalous upturn below 11 K, which persists in presence of magnetic field even up to 14 T. In the low-temperature region, the resistivity upturn exhibits a unique $T^{1/2}$ scaling behavior, which remains unchanged when an external magnetic field is applied. The $T^{1/2}$ dependence of resistivity upturn is the hallmark of non-Fermi liquid state in orbital two-channel Kondo effect. This anomalous resistivity upturn in ${\mathrm{Co}}_{0.28}{\mathrm{TaS}}_2$ can be attributed to the orbital two-channel Kondo mechanism.

The collective excitations of solids are classified as longitudinal and transverse depending on their relative polarization and propagation direction. This seemingly formal classification results in surprisingly distinct types of excitations if calculated within the Coulomb gauge. Transverse modes couple to free-space photons and hybridize into polaritons for strong light-matter coupling. Longitudinal modes, in contrast, are seen as pure matter excitations that produce a dynamic polarization inside the material without photon coupling. Here we show that both longitudinal and transverse modes manifest as polaritons in the explicitly covariant Lorenz gauge. Longitudinal excitations couple to longitudinal and scalar photons, which have been considered elusive so far. We show that the dipolar excitations become systematically threefold degenerate in the long-wavelength limit when including all photonic degrees of freedom, as expected from symmetry. Our findings demonstrate how choosing a gauge determines our thinking about materials excitations and how gauge fixing reveals new pathways for tailoring polaritons in crystals, metamaterials, and surfaces. Longitudinal polaritons will interact with longitudinal near fields located at surfaces, which provides additional excitation channels to engineer scanning near-field microscopy and surface-enhanced spectroscopy.

We introduce a one-dimensional (1D) extended quantum breakdown model comprising a fermionic and a spin degree of freedom per site, and featuring a spatially asymmetric breakdown-type interaction between the fermions and spins. Our model resembles the breakdown process of particles incident into a cloud chamber with nonzero quantum amplitudes of both exciting and not exciting the local vapor atoms. We analytically show that, in the absence of any magnetic field for the spins, the model exhibits Hilbert space fragmentation within each symmetry sector into exponentially many Krylov subspaces and hence displays nonthermal dynamics. Here, we demonstrate that the fragmentation naturally occurs in an entangled basis and thus provides an example of “quantum fragmentation.” Besides establishing the nature of fragmentation analytically, we also study the long-time behavior of the entanglement entropy and its deviation from the expected Page value as a probe of ergodicity in the system. Upon introducing a magnetic field for the spins, most of the Krylov subspaces merge and the model becomes chaotic. Finally, we study the effects of strong randomness on the system and observe behavior similar to that of many-body localized systems.