A recent experimental study of $\mathrm{Tb}{\mathrm{B}}_4$ at a low temperature using resonant x-ray Bragg diffraction implies a magnetic symmetry not found in any other rare-earth tetraboride. The evidence for this assertion is a change in the intensity of a $\mathrm{Tb}{\mathrm{B}}_4$ Bragg spot on reversing the handedness (chirality) of the primary x-ray beam [R. Misawa, K. Arakawa, T. Yoshioka, H. Ueda, F. Iga, K. Tamasaku, Y. Tanaka, and T. Kimura, Phys. Rev. B 108, 134433 (2023)]. It reveals a magnetic chiral signature in $\mathrm{Tb}{\mathrm{B}}_4$ that is forbidden in phases of rare-earth tetraborides known to date, as the previous magnetic symmetries are parity-time (PT) symmetric with anti-inversion present in the magnetic crystal class. Misawa et al. appeal to a PT-symmetric diffraction pattern to interpret their interesting diffraction patterns. In addition to the use of symmetry that does not permit a chiral signature, calculated patterns impose cylindrical symmetry on Tb sites with no justification. We review magnetic symmetries for $\mathrm{Tb}{\mathrm{B}}_4$ consistent with a published neutron powder diffraction pattern and susceptibility measurements. On the basis of this information, noncollinear antiferromagnetic order exists below a temperature $\approx 44$ K with no ferromagnetic component. Our symmetry-informed patterns encapsulate Tb electronic degrees of freedom in terms of multipoles consistent with established sum rules for dichroic signals. The investigated symmetry templates are noncentrosymmetric, noncollinear antiferromagnetic constructions with propagation vector $\mathbf{k}=\left(0,0,0\right)$. An inferred chiral signature for a parity-even absorption event has an interesting composition. There is the anticipated product of Tb axial dipoles and chargelike quadrupoles (from Templeton-Templeton scattering). Beyond this contribution, though, symmetry allows a product of dipoles in the chiral signature. A predicted change in the intensity of a Bragg spot with rotation of the crystal about the reflection vector (an azimuthal angle scan) can be tested in future experiments. Likewise contributions to Bragg diffraction patterns from Tb anapoles and higher-order Dirac multipoles.

The magnon current holds substantial importance in facilitating the transfer of angular momentum in spin-based electronics. However, the magnon current in three-dimensional magnetic materials remains orders of magnitude too small for applications. In contrast, magnon numbers in two-dimensional systems exhibit significant enhancement and are markedly influenced by external magnetic fields. Here, we investigate the magnon current in a two- dimensional easy-axis ferromagnet and find a large magnon magnetoresistance (LMMR) effect, wherein the change of the magnon conductance can reach as high as a thousand percent in a moderate magnetic field. Moreover, the magnitude of the LMMR exhibits significant dependence on the orientation of the magnetic field due to the interplay between magnon-conserving and non-magnon-conserving scattering. We propose a nonlocal magnon-mediated electrical drag experiment for the possible experimental observation of the predicted effect. With the LMMR effect and a much larger magnon number, magnon current in 2D materials shows promise as a primary source for spin transport in spintronics devices.

The $\mathrm{F}{\mathrm{e}}_3\mathrm{Ga}$ alloy with $D{0}_3$ phase has been reported to exhibit remarkable anomalous transport properties arising from the topological nontrivial nodal lines. In this study, the effect of Mn doping on the magnetic, electronic, and anomalous transport properties of polycrystalline $\mathrm{F}{\mathrm{e}}_{3-x}\mathrm{M}{\mathrm{n}}_x\mathrm{Ga}$ ($x=0$, 0.4, 0.6, and 1) are investigated. As the Mn doping level increases, the saturated magnetization at 10 K gradually decreases, while the anomalous Hall resistivity ${\rho }_{xy}^A$ shows a significant increasing trend, reaching a maximum value of 7.2 µΩ cm in $\mathrm{F}{\mathrm{e}}_2\mathrm{MnGa}$. The analysis of anomalous Hall effect (AHE) based on the expanded scaling mechanism proposed by Tian et al. [Phys. Rev. Lett. 103, 087206 (2009)] suggests that the AHE in $\mathrm{F}{\mathrm{e}}_3\mathrm{Ga}$ is dominated by intrinsic mechanism, with an intrinsic anomalous Hall conductivity (${\sigma }_{xy}^{\mathrm{int}}$) of 288 S/cm. In samples with $x=0.4$, extrinsic impurity and phonon scattering cannot be neglected and ${\sigma }_{xy}^{\mathrm{int}}$ decreases to 174 S/cm. As $x$ increases to 0.6, the intrinsic mechanism vanishes and the extrinsic impurity and phonon-scattering mechanisms become dominant in the AHE. A further enhanced extrinsic scattering in the AHE is observed in $\mathrm{F}{\mathrm{e}}_2\mathrm{MnGa}$ at low temperature with an anomalous Hall conductivity of 237 S/cm at 10 K. From ab initio calculations, we notice a ${\sigma }_{xy}^{\mathrm{int}}$ peak of 2310 S/cm locates approximately −0.5 eV below Fermi level ($E_{\mathrm{F}}$) in $\mathrm{F}{\mathrm{e}}_3\mathrm{Ga}$ alloy, originating from the six linked nodal rings. When one Fe atom is substituted by Mn, this peak shifts to 0.5 eV above $E_{\mathrm{F}}$ in $\mathrm{F}{\mathrm{e}}_2\mathrm{MnGa}$. We propose that partially doping Fe with Mn in $\mathrm{F}{\mathrm{e}}_3\mathrm{Ga}$ may tailor the large peak of ${\sigma }_{xy}^{\mathrm{int}}$ around $E_{\mathrm{F}}$.

We report precise measurements to obtain the normal-state resistivity and the depairing current density of ${\mathrm{BaFe}}_2{\left({\mathrm{As}}_{1-x}{\mathrm{P}}_x\right)}_2(x\sim 0.29-0.32)$ nanobridges along the $c$ axis, by using focused ion beam (FIB) techniques. We obtained both of the $ab$-plane and $c$-axis resistivity $({\rho }_{ab}$ and ${\rho }_c)$ in the same part of a specimen, by fabricating the $c$-axis nanobridge in the middle of a narrow bridge extended in the $ab$ plane, in spite of the slight deficiency of P dopant due to the additional FIB fabrication. The normal-state resistivity anisotropy agreed with the previous results for bulk samples, showing ${\rho }_c/{\rho }_{ab}<8$ just above the superconducting transition temperature, $T_c$, in the slightly underdoped region and a slight decrease with increasing temperatures. The critical current density obtained in the $c$-axis nanobridges near the optimal doping reaches $\sim 8$ $\mathrm{MA}/{\mathrm{cm}}^2$ at $0.15T_c$, corresponding to about 87% of a depairing limit derived by the Eilenberger equations. An extrapolation to $T=0$ K using the Ginzburg-Landau model suggests that the anisotropy of the depairing current density roughly corresponds to that of the normal-state resistivity. At low temperatures, we also observed a steplike voltage jump before arriving at the depairing limit, suggesting the occurrence of phase-slip phenomena near the depairing processes.

The ${\mathrm{NbSe}}_2$ monolayer with Rashba spin-orbit coupling represents a paradigmatic example of an Ising superconductor on a substrate. Using a single-band model and symmetry analysis, we present general superconducting pairing functions beyond the nearest-neighbor approximation, uncovering new types of gap functions, including the nodal singlet gap function and the triplet nonunitary pairing function that breaks time-reversal symmetry. The nonunitarity builts in the asymmetrical band dispersion in the superconducting quasiparticle energy spectra. Performing exact $T$-matrix calculations of quasiparticle interference due to a single scalar impurity scattering, we found that the interference patterns possess characteristic features distinguishing the type of pairing and possible nematic and chiral symmetry violations.

Intrinsic Rashba spin-orbital coupling (SOC) can exist in centrosymmetric materials with local inversion symmetry breaking. Here we show that such a SOC can induce topological superconductivity together with an in-plane Zeeman field in planar Josephson junctions formed by the centrosymmetric materials. A single Majorana mode can be created at each end of the junction. We demonstrate this result in a model respecting the same symmetry group with the iron-based superconductors. We derive the necessary Fermi surface condition for the topological planar junction and calculate the topological phase diagram with respect to the in-plane Zeeman field and the phase difference between the two superconductors. We provide experimental characteristics for the topological superconductivity, including the differential conductance and the Fano factor tomography which can be measured in the scanning tunneling spectroscopy. Our study reveals that the centrosymmetric systems with local-inversion-symmetry breaking can serve as new platforms for the topological planar Josephson junctions and helps to find more experimentally feasible materials for the topological superconductors.

We study the physics of the strong-coupling Hubbard model in a kagome lattice ribbon under mechanical tension and half filling. It is known that in the absence of strain, the lattice symmetry of the system and strong electronic interactions induce magnetic frustration. As uniaxial strain is applied, the ribbon exhibits various configurations with energy oscillations that depend on the direction of the strain axis. The ground states are obtained by density-matrix renormalization-group calculations. We find that the system is characterized by strong antiferromagnetic bonds distributed throughout the lattice in directions and patterns that depend on the strain directions and may coexist with easily polarizable sites that are only weakly correlated to their neighbors. We identify frustration and correlation measures that follow the strain and interaction dependence of the system well. These results illustrate that strain-dependent magnetic susceptibility could be explored experimentally to help probe the role of symmetry and interactions in these systems.

The analysis of phase transitions of gauge theories has relied heavily on simplifications that arise at the boundaries of phase diagrams, where certain excitations are forbidden. Taking $2+1$-dimensional ${\mathbb{Z}}_2$ gauge theory as an example, the simplification can be visualized geometrically: on the phase diagram boundaries the partition function is an ensemble of closed membranes. More generally, however, the membranes have “holes” in them, representing worldlines of virtual anyon excitations. If the holes are of a finite size, then typically they do not affect the universality class, but they destroy microscopic (higher-form) symmetries and microscopic (string) observables. We demonstrate how these symmetries and observables can be restored using a “membrane patching” procedure, which maps the ensemble of membranes back to an ensemble of closed membranes. (This is closely related to the idea of gauge fixing in the “minimal gauge,” though not equivalent.) Membrane patching makes the emergence of higher symmetry concrete. Performing patching in a Monte Carlo simulation with an appropriate algorithm, we show that it gives access to numerically useful observables. For example, the confinement transition can be analyzed using a correlation function that is a power law at the critical point. We analyze the quasi-locality of the patching procedure and discuss what happens at a self-dual multicritical point in the gauge-Higgs model, where the lengthscale $\ell$ characterizing the holes diverges. The patching approach described here generalizes to many other statistical ensembles with a representation in terms of fluctuating membranes or loops, in various dimensions, and related constructions could be implemented in experiments on quantum devices.

We study the high-harmonic generation (HHG) in the Aubry-Andre-Harper (AAH) model. The modulating phase of the AAH model is used as a control parameter while preserving the chiral symmetry hosting the zero-energy edge states. The harmonic yield in a particular energy range exhibits a strong dependence on the control parameter with a clear separation of the region of topologically trivial and nontrivial phases of the system. The threshold for the harmonic yield is found to serve as an all-optical tool for detecting topological phases. We extended our study with broken chiral symmetry by including the onsite potential. The introduction of the onsite potential lifts the degeneracy in the edge states, which affects the harmonic enhancement. Furthermore, it is also observed that the system's onsite strength can control the HHG yield.

We investigate the anomalous photoinduced band renormalization in correlated materials, exemplified by the case of ${\mathrm{Ta}}_2{\mathrm{NiSe}}_5$. The manifestation of this anomaly is characterized by the alternating direction of band shift in response to changes in the laser parameters or electron momentum. We attribute the phenomena to the band inversion of the material and the selective excitation of a high-lying flat band, leading to the competition between the Hartree shift and the order collapse. These findings are based on an ab initio determined effective model for ${\mathrm{Ta}}_2{\mathrm{NiSe}}_5$, in which we incorporate high-lying states and the time-dependent $GW$ simulation to follow the nonequilibrium dynamics induced by the laser. Our findings reveal the sensitivity of the nonequilibrium electronic dynamics to the band structure and laser protocols, providing valuable guidance for the selection of suitable materials and lasers in the engineering of band structures.

In optical lattices attractive ultracold fermions with three hyperfine-spin components (colors) can form three fermionic configurations depending on the interactions—unbound fermions, on-site trions, and off-site trions—leading to the coexistence of multiple fermionic species in the ordered phase, which demonstrates that the attractive three-color fermions are unique from other correlated fermion systems and may host intriguing phases and phase transitions. At temperatures below the superexchange energy scale, we employ the determinant quantum Monte Carlo (QMC) method to investigate the phases and phase transitions in the half-filled attractive three-color Hubbard model on a honeycomb lattice where the Hubbard interactions are color dependent (anisotropic interactions) and the coupling between color 3 and colors (1, 2) serves as a control parameter. In the coupling regime where on-site and off-site trions coexist, our QMC simulations demonstrate coexisting Néel and charge density wave (CDW) orders which are common in condensed matter but rare in ultracold atoms. At weak coupling where the color superfluid (CSF) order is scattered by color-3 fermions, we find that very small coupling of color 3 with colors (1, 2) can destroy the CSF order and that the vanishing of the CSF order is not immediately accompanied by the emergence of the on-site trionic phase, which strikingly disagrees with the prevalent results of dynamical mean-field theory. The underlying mechanisms of the coexisting Néel/CDW orders and of the CSF order breaking are also presented based on intuitive physical pictures.

Although nonsymmorphic symmetry protects ${\mathbb{Z}}_4$ topology for Hermitian systems, non-Hermitian topological phenomena induced by such a unique topological structure remain elusive. In this paper, we elucidate that systems with glide symmetry exhibit non-Hermitian skin effects (NHSE) characterized by ${\mathbb{Z}}_4$ topology. Specifically, numerically analyzing a two-dimensional toy model, we demonstrate that the ${\mathbb{Z}}_4$ topology induces the NHSE when the topological invariant takes $\nu =1$ and 2. Furthermore, our numerical analysis demonstrates that the NHSE is destroyed by perturbations preserving the relevant symmetry when the ${\mathbb{Z}}_4$ invariant takes $\nu =4$.

Spin-preserving chiral mirrors, which reflect only one spin state of light under normal illumination without reversing the light's handedness, are intrinsically chiral structures. These mirrors are of particular interest for applications in optical imaging, chiral quantum optics, chiral cavities, and the recognition and sensing of chiral molecules. However, most of them are limited by complicated chiral elements of their unit cells and multilayer structures, which are challenging to fabricate and integrate in the visible-near-infrared region. Here we propose a thin monolithic photonic crystal (PhC) mirror with elliptical air holes to realize a giant intrinsic chiroptical response. Beyond the past chiral mirrors, our chiral mirrors selectively reflect only one spin state of light while preserving its handedness, exhibiting a near unity of circular dichroism (CD). The working principle of the PhC chiral mirror is based on guided-mode resonance with the simultaneous excitation of transverse electric (TE) and transverse magnetic (TM) eigenmodes. Interestingly, the TE and TM bands can be dynamically adjusted via the orientation angle of the elliptical air holes, leading to their degeneracy at a certain orientation angle. Based on the modified coupled mode theory, we show that the key point to achieving giant intrinsic CD is the angular difference in the in-plane effective orientation of the TE and TM eigenmode currents. As a proof of concept, we designed such an easy-fabrication PhC to serve as a spin-preserving chiral mirror, which shows superiority to the previously reported structure. The results of this work may provide new possibilities for compact chiral sensing, imaging, and polarization-sensitive devices.

We perform simulations for transport and nontrivial fusion of Majorana zero modes in topological superconducting quantum wires. We uncover interesting behaviors of nonadiabatic transition associated with the transport through mini-gate-controlled multiple-segment modulations. Owing to breaking of the initial fermion parity induced by nonadiabatic transitions, a deviation from the statistics of outcomes of nontrivial fusion arises and is analyzed. Moreover, we develop a measurement scheme to infer the amount of fermion parity breaking and nonadiabatic transition probability to excited states, based on the characteristic spectrum of measurement current by a quantum-point-contact detector, by measurement of the charge occupation dynamics in a fusion-outcome-probing quantum dot.

We consider a non-Hermitian (NH) analog of a second-order topological insulator, protected by chiral symmetry, in the presence of next-nearest-neighbor hopping elements to theoretically investigate the interplay beyond the first-nearest-neighbor hopping amplitudes and topological order away from Hermiticity. In addition to the four zero-energy corner modes present in the first-nearest-neighbor hopping model, we uncover that the second-nearest-neighbor hopping introduces another topological phase with 16 zero-energy corner modes. Importantly, the NH effects are manifested in altering the Hermitian phase boundaries for both of the models. While comparing the complex energy spectrum under open boundary conditions, and bi-orthogonalized quadrupolar winding number in real space, we resolve the apparent anomaly in the bulk boundary correspondence of the NH system as compared to the Hermitian counterpart by incorporating the effect of the non-Bloch form of momentum into the mass term. The above invariant is also capable of capturing the phase boundaries between the two different topological phases where the degeneracy of the corner modes is evident, as exclusively observed for the second-nearest-neighbor model.

We present a two-dimensional model of a fermionic wire which shows a power-law conductance behavior despite the presence of uncorrelated disorder along the direction of the transport. The power-law behavior is attributed to the presence of energy eigenstates of diverging localization length below some energy cutoff, $E_c$. To study transport, we place the wire in contact with electron reservoirs biased around a Fermi level, $E$. We show that the conductance scales superdiffusively for $\left|E\right|<E_c$ and decays exponentially for $\left|E\right|>E_c$. At $\left|E\right|=E_c$, we show that the conductance scales diffusively or with different subdiffusive power laws, depending on the sign of the expectation value of the disorder and the parameters of the wire.

Plasmons and polar phonons are elementary electrodynamic excitations of matter. In two dimensions and at long wavelengths, they couple to light and act as the system polaritons. They also dictate the scattering of charged carriers. Van der Waals heterostructures offer the opportunity to couple excitations from different layers via long-range Coulomb interactions, modifying both their dispersion and their scattering of electrons. Even when the excitations do not couple, they are still influenced by the screening from all layers, leading to complex dynamical interactions between electrons, plasmons, and polar phonons. We develop an efficient ab initio model to solve the dynamical electric response of Van der Waals heterostructures, accompanied by a formalism to extract relevant spectroscopic and transport quantities. Notably, we obtain scattering rates for electrons of the heterostructure coupling remotely with electrodynamic excitations. We apply those developments to BN-capped graphene, in which polar phonons from BN couple to plasmons in graphene. We study the nature of the coupled excitations, their dispersion and their coupling to graphene's electrons. Regimes driven by either phonons or plasmons are identified, as well as a truly hybrid regime corresponding to the plasmon-phonon-polariton at long wavelengths. Those are studied as a function of the graphene's Fermi level and the number of BN layers. In contrast with standard descriptions in terms of surface-optical phonons, we find that the electron-phonon interaction stems from several different modes. Moreover, the dynamical screening of the coupling between BN's LO phonons and graphene's electrons crosses over from inefficient to metal-like depending on the relative value of the phonons' frequency and the energetic onset of interband transitions. While the coupling is significant in general, the associated scattering of graphene's carriers is found to be negligible with respect to the particularly large one coming from intrinsic phonons in the context of electronic transport.

Introducing hydrogen bonds into the structure of amorphous silicon nitride ($a\text{−}\mathrm{Si}{\mathrm{N}}_x$:H) is attractive for dielectrics seeking extremely low thermal conductivity. Yet, experimental explorations of enhancing diffuson scattering are still insufficient. Here, $a\text{−}\mathrm{Si}{\mathrm{N}}_{0.91}$:H films containing $(25\pm 5)\%$ hydrogen as well as control samples of hydrogen-free $a\text{−}\mathrm{Si}{\mathrm{N}}_{0.96}$ films were characterized using microbelt thermal bridge devices. The capability of employing a transfer length method to extract intrinsic thermal conductivity was demonstrated. Unusual thermal contact resistances and diffuson transfer lengths were corroborated, which provided evidence of diffuson crowding phenomena at bridge-end homojunctions. Two distinct features, including diffuson population-dictated thermal conductivity at low temperature and diffuson scattering-dominant thermal conductivity at high temperature were revealed. The effect of a hydrogen heavily-incorporated structure showed that room temperature thermal conductivity of $a\text{−}\mathrm{Si}{\mathrm{N}}_{0.91}$:H is largely suppressed to $0.8\pm 0.1\mathrm{W}/\left(\mathrm{m}\mathrm{K}\right)$, compared with $1.8\pm 0.3\mathrm{W}/\left(\mathrm{m}\mathrm{K}\right)$ of hydrogen-free $a\text{−}\mathrm{Si}{\mathrm{N}}_{0.96}$.

In the cuprates, the opening of a $d$-wave superconducting (SC) gap is accompanied by a redistribution of spectral weight at energies two orders of magnitude larger than this gap. This indicates the importance to the pairing mechanism of on-site electronic excitations, such as orbital transitions or charge transfer excitations. Here, we resort to a three-pulse pump-probe scheme to study the broadband nonequilibrium dielectric function in optimally doped $\mathrm{B}{\mathrm{i}}_2\mathrm{S}{\mathrm{r}}_2\mathrm{C}{\mathrm{a}}_{0.92}{\mathrm{Y}}_{0.08}\mathrm{C}{\mathrm{u}}_2{\mathrm{O}}_{8+\delta }$ and we identify an interband excitation peaked at 2 eV whose spectral weight is transiently modified by the pump. Photoexcitation with near-infrared and midinfrared pulses, with photon energies, respectively, above and below the SC gap, reveals that the spectral weight dynamics is different for different pump wavelengths and depends on the time order of the two photoexcitations. The picture that emerges is that, while high-energy pulses excite quasiparticles in both nodal and thermally inaccessible antinodal states, photoexcitation by low-energy pulses mostly accelerates the condensate and creates excitations predominantly at the nodes of the SC gap. These results, rationalized by simulations based on the kinetic equations for $d$-wave superconducting gaps, indicate that dynamical control of the momentum-dependent distribution of nonthermal quasiparticles may be achieved by the selective tuning of the photoexcitation.