We studied magnetic-field responses of a low-symmetrical site, i.e., an orthorhombic site in a tetragonal crystal, in ${\mathrm{Ce}}_2{\mathrm{Pd}}_2\mathrm{Pb}$, which exhibits a strong axial moment in the cerium site. Considering two orthogonalized local-coordinate systems on the cerium site, the field responses of the moment can be expressed as a product of the external field and spatial variation of the $g$ factor and be regarded as the responses of an effective staggered field for the isotropic pseudospin $s_{\mathrm{p}}=1/2$ state. We obtained $H\text{−}T$ phase diagrams of ${\mathrm{Ce}}_2{\mathrm{Pd}}_2\mathrm{Pb}$ under the fields $H\parallel \langle 100\rangle$ and $H\parallel \langle 110\rangle$ from thermodynamic measurements and identified magnetization plateaus for several phases. Assuming the effective staggered field, we can explain the specific heat of ${\mathrm{Ce}}_2{\mathrm{Pd}}_2\mathrm{Pb}$ under high fields. The result indicates that a partially ordered state in which one-half of the total cerium moments contributes to the long-range order is realized for $H\parallel \langle 110\rangle$, where the staggered component becomes maximum. Furthermore, a slight incline of the field results in a change in the ordering nature of the partially ordered phase, demonstrating the controllability of the effective staggered field.

A recent ab initio investigation of Na-C binary compounds under moderate pressures has uncovered a possible stable ${\mathrm{NaC}}_4$ superconductor with an estimated critical temperature up to 41 K. We revisit this promising binary system by performing a more focused exploration of Na-intercalated graphite configurations, assessing the sensitivity of their thermodynamic stability to density functional approximations at different $(T,P)$ conditions, and examining their superconducting properties with the Migdal-Eliashberg formalism. The combinatorial screening of possible Na arrangements reveals additional stable stoichiometries, i.e., ${\mathrm{Na}}_3{\mathrm{C}}_{10}, {\mathrm{NaC}}_8, {\mathrm{NaC}}_{10}$, and ${\mathrm{NaC}}_{12}$, that redefine the previously proposed convex hulls for pressures up to 10 GPa. The evaluation of formation enthalpies with different van der Waals functionals indicates that the proposed compounds might not be thermodynamically stable at zero temperature but some of them could stabilize due to the vibrational entropy or form via cold compression if graphite is used as a starting material. Our more rigorous modeling of the electron-phonon coupling in ${\mathrm{NaC}}_4$ confirms the material's potential for high-temperature superconductivity, with a critical temperature reaching 48 K at 10 GPa, and reveals a well-defined two-gap structure unusual for an electron-doped compound. By tracking the position of the intercalant nearly free electron states with respect to the Fermi level in viable Na-C compounds, we map out the range of pressures and compositions needed for strong electron-phonon coupling and identify ${\mathrm{Na}}_3{\mathrm{C}}_{10}$ as an equally promising superconductor.

In the absence of time-reversal invariance, metals without inversion symmetry may exhibit nonreciprocal charge transport—a magnetochiral anisotropy that manifests as unequal electrical resistance for opposite current flow directions. If superconductivity also sets in, then the charge transmission may become dissipationless in one direction while remaining dissipative in the opposite, thereby realizing a superconducting diode. Through both direct-current and alternating-current measurements, we study the nonreciprocal effects in thin films of the noncentrosymmetric superconductor $T_d\text{−}{\mathrm{MoTe}}_2$ with disorder. We observe nonreciprocal superconducting critical currents with a diode efficiency close to 20%, and a large magnetochiral anisotropy coefficient up to $5.9\times {10}^8{\mathrm{T}}^{-1}{\mathrm{A}}^{-1}$, under weak out-of-plane magnetic field in the millitesla range. The great enhancement of rectification efficiency under out-of-plane magnetic field is likely ascribed to the vortex ratchet effect, which naturally appears in the noncentrosymmetric superconductor with disorder. Intriguingly, unlike the finding in Rashba systems, the strongest in-plane nonreciprocal effect does not occur when the field is perpendicular to the current flow direction. We develop a phenomenological theory to demonstrate that this peculiar behavior can be attributed to the asymmetric structure of spin-orbit coupling in $T_d\text{−}{\mathrm{MoTe}}_2$. Our study highlights how the crystallographic symmetry critically impacts the nonreciprocal transport, and would further advance the research for designing the superconducting diode with the best performance.

This study presents a joint first-principles and experimental investigation of the thermophysical properties of liquid zirconium at high temperatures. An ab initio estimate of the critical point parameters of zirconium is obtained: $T_c=9.4\pm 0.1\mathrm{kK}$, ${\rho }_c=1.38\pm 0.1\mathrm{g}/{\mathrm{cm}}^3$, and $P_c=3.35\pm 0.4$ kbar. In addition, we analyze various thermodynamic properties, including thermal expansion, isochoric and isobaric heat capacity, the Grüneisen parameter, and the speed of sound in liquid zirconium along the critical isobar, providing approximation dependencies that align with experimental measurements. We also present a tabulated ab initio equation of state for Zr in the liquid and supercritical regions. Experimental data from rapid electrical pulse heating of zirconium wires confirm the low fusion enthalpy and the isobaric heat capacity dependence predicted by our quantum molecular dynamics (QMD) simulations. The resistivity of solid and liquid zirconium up to 6 kK is also measured and its significant increase in the critical region is shown using the Kubo-Greenwood formula. Calculated normal spectral emissivity shows almost constant behavior up to 4 kK with a significant increase at higher temperatures.

Interactions between particles normally induce the decay of the particles Bloch oscillations (BOs) in a periodic lattice. In the limit of strong on-site interactions, spin-$1/2$ fermions may form doublon bound states and undergo BOs in the presence of a tilted potential. Here we investigate the impact of nearest-neighbor interaction $V$ on the multidoublon BOs in a mass-imbalanced extended Fermi-Hubbard model. We derive an effective Hamiltonian for doublons, and show that a slight change in $V$ can qualitatively alter their dynamic behaviors. Notably, at a resonance point, the doublons behave like free hard-core bosons. Under a tilted potential, the system may exhibit different types of multidoublon BOs at or deviation from the resonance point. Numerical results are presented to demonstrate our conclusions in both one- and two-dimensional systems.

Magnon dynamics in skyrmion lattices have garnered significant interest due to their potential applications in topological magnonics. Existing theories often follow a single-momentum approach, assuming significant Dzyaloshinskii-Moriya interaction (DMI) to minimize the skyrmion's dimensions, which can lead to oversimplification in describing magnon behavior. This study introduces a multimomentum operator theory for magnons in realistically large two-dimensional skyrmions, where each skyrmion encompasses several thousand spins. The proposed theory fully transforms the magnon Hamiltonian into momentum space, incorporating off-diagonal terms to capture umklapp scattering caused by the skyrmion wave vectors. Our results reveal deviations from single-momentum theories, demonstrating that flat bands are not universal features of the skyrmionic magnon spectrum. Additionally, we find that manipulating the skyrmion size with an external magnetic field induces multiple topological phase transitions. At high magnetic fields, the low-energy magnon spectrum becomes densely packed and entirely topological, resembling a topological band continuum.

The spin-$3/2$ chain is a versatile prototypical platform for the study of competition between different kinds of magnetic orders, with the objective of obtaining a deeper understanding of the corresponding quantum phase transitions. In this work, we investigate the spin-$3/2$ chain with nearest-neighbor $J_1$, next-nearest-neighbor $J_2$, and uniaxial single-ion anisotropy $D$ terms in the absence of a magnetic field. For positive values of $J_2/J_1$ and $D/J_1$, we find seven different phases in a rich phase diagram. Without frustration $J_2=0$, a gapless Luttinger liquid phase remains stable for all $D>0$. As $J_2$ increases, we observe three phases with distinct dimerized valence bond orders, which show an intricate competition with vector chiral order and incommensurate correlations. For large $J_2$, regions of phase coexistence between the dimerized and vector chiral orders emerge. We present large-scale numerical data for the determination of transition lines, order parameters, and the nature of the phase transitions.

Despite many years studies, there is still a significant discrepancy between the first-principles calculations and experimental measurements of platinum's optical properties in the existing literature. In this work, we explain the reason for this discrepancy by combining spectroscopic ellipsometry (SE) measurements and density functional theory (DFT) calculations. Pt films were fabricated by electron beam physical vapor deposition, and their properties were measured with SE. The dielectric function and consequently plasma frequency, relaxation constant, and interband spectra were then retrieved using the Drude-Lorentz model. DFT calculations of plasma frequency and interband contribution (Lorentz part) in random-phase approximation show a good match between the experimental and theoretical parameters, providing valuable insights into the electronic and optical properties of platinum. The effect of possible defects is studied with DFT as well. The data for the dielectric function of platinum is tabulated in the spectral range of 200–3500 nm and offers important implications for its potential applications in optoelectronic devices and plasmonic systems. The long-standing discrepancy between theory and experiment is explained by insufficient and inaccurate data in the infrared region of the spectrum, which is important for reliable separation of inter and intraband transition contributions to the spectrum and determination of the plasma frequency.

We demonstrate that the ground-state energy band of an extended one-dimensional Holstein model, featuring a specific type of nonlinear electron-phonon coupling for a single electron in the band, is exactly solvable. Numerical results indicate that, despite the significant differences in electron-phonon coupling between the extended Holstein model and the original Holstein model, the ground-state energy of the Holstein model can be accurately reproduced by the extended model through appropriate rescaling of the coupling parameter. Additionally, for an $N$-site lattice, there are $2^{N-1}$ distinct choices for the set of parameters in the nonlinear electron-phonon coupling, all yielding the same ground-state energy but with varying ground-state properties. This flexibility allows for the selection of the optimal parameter set in the extended model to best simulate the ground-state properties of the system.

The electronic and crystal structures of ${\mathrm{YbCu}}_x{\mathrm{Ga}}_{2-x}$ under pressure were investigated by high-resolution x-ray absorption spectroscopy (XAS) at the Yb-$L_3$ absorption edge and x-ray diffraction. A rapid valence transition was found in ${\mathrm{YbCu}}_{0.5}{\mathrm{Ga}}_{1.5}$ around 5 GPa accompanying the structural phase transition. In YbCuGa and ${\mathrm{YbCu}}_{1.5}{\mathrm{Ga}}_{0.5}$ the Yb valence increased gradually up to 5–7 GPa and 16 GPa with pressure, respectively, and did not show a significant change above those pressures. XAS study at the Cu-$L$ absorption edge was also performed. The major hybridization partner of Yb $4f$ electrons switched from Ga to Cu with increasing the Cu content around $x=1$–1.5, where the $c$–$f$ hybridization was weakest. Photoelectron spectroscopy was performed around Yb $4d$–$4f$ resonance energy and at 8.4 eV.

We investigate the transport properties of a quantum wire of weakly interacting fermions in the presence of local particle loss. We calculate current and conductance in this system due to applied external chemical potential bias that can be measured in experimental realizations of ultracold fermions in quasi one-dimensional traps. Using a Keldysh field theory approach based on the Lindblad equation, we establish a perturbative scheme to study the effect of imbalanced reservoirs. Logarithmically divergent terms are resummed using a renormalization group method, and a novel powerlaw behavior for the conductance as a function of the potential bias across the wire is found. In contrast to the equilibrium case of a potential barrier in a Luttinger liquid, the conductance exhibits a scaling behavior, which depends on the interaction strength and on the loss probability. Repulsive interactions reduce the conductance of the wire while attractive interactions enhance it. However, perfect reflectivity and transparency are only reached in the absence of particle loss.

We introduce diagnostics of the transition between the ergodic and many-body localization phases, which are based on complexity measures defined via the probability distribution function of the Lanczos coefficients of the tridiagonalized Hamiltonian. We use these complexity measures to analyze the power-law random banded matrix model as a function of the correlation strength and show that the moments and the entropy of the distribution diagnose the ergodic to many-body transition, as well as the distinctive feature of the phases concerning the memory of the initial conditions.

The coalescence of eigenstates is a unique phenomenon in non-Hermitian systems. Remarkably, it has been noticed in some non-Hermitian systems under open boundary conditions that the whole set of eigenstates can coalesce to only a few eigenstates. In the parameter space, the point at which such a coalescence of macroscopic eigenstates occurs is dubbed as an infernal point. In this Letter, based on the non-Bloch band theory and amoeba formulation, we establish the criteria for the presence of infernal points in one-dimensional and higher-dimensional open boundary non-Hermitian systems. In addition, we find an explanation for the extreme localization of the wave functions and unveil the mechanism for the coalescence of enormous eigenstates at the infernal points. Our work provides a general theory for infernal points in open boundary non-Hermitian systems in arbitrary dimensions, and hence paves the way to study the intriguing infernal points systematically.

In AB-stacked bilayer graphene, the introduction of an out-of-plane electric field can break the inversion symmetry to open up a nontrivial bulk gap hosting the quantum valley Hall state. However, in ABA-stacked trilayer graphene, the out-of-plane electric field cannot open up a nontrivial valley band gap. By applying a pair of antiparallel electric fields, we theoretically propose three kinds of schemes to open up bulk gaps that harbor the quantum valley Hall effect in the ABA-stacked trilayer graphene. By further considering the small-angle twisted trilayer graphene, we can obtain the topological confinement states along the naturally formed domain walls between ABA- and BAB-stacked regions. It is noteworthy that the synergic effect between the antiparallel electric fields and the magnetic field can open up a nontrivial band gap possessing the quantum valley Hall effect and quantum Hall effect simultaneously. Our work not only theoretically proposes how to realize the quantum valley Hall effect in ABA-trilayer graphene, but also provides an ideal platform to explore the hybrid topological phases.

${\mathrm{SrTiO}}_3$ is an incipient ferroelectric and an exceptionally dilute superconductor with a domelike dependence on carrier concentration. Stabilization of a polar phase through chemical substitution or strain significantly enhances the superconducting critical temperature, suggesting a possible connection between the polar instability and unconventional Cooper pairing. To investigate the effects of doping on the polar order in ${\mathrm{SrTiO}}_3$, we develop a simplified free-energy model which includes only the degrees of freedom necessary to capture the relevant physics of a doped, biaxially compressively strained system. We simulate the polar and antiferrodistortive thermal phase transitions using Monte Carlo methods for different doping levels and comment on the doping dependence of the transition temperatures and the formation of polar nanodomains. In addition, the temperature-dependent phonon spectral function is calculated using Langevin simulations to investigate the lattice dynamics of the doped system. We also examine the effects of doping on the electronic structure within the polar phase, including the density of states and band splitting. Finally, we compute the polarization dependence of the Rashba parameter and the doping dependence of the Midgal ratio, and place our results in the broader context of proposed pairing mechanisms.

We introduce a retrieval method for determining the equivalent material parameters of linear metasurface stacks for excitation at arbitrary incidence angles. Leveraging auxiliary tensors analytically formulated from the constitutive parameter tensors, we establish a connection between the homogenization parameters of two-dimensional metasurfaces and their three-dimensional stacked counterparts. These equivalent parameters are shown to replicate the scattering behavior of the metasurface stack accurately and highlight the role of nonlocality in these problems. We validate our method through numerical simulations of four distinct examples. In this paper, using our approach, we not only shed light on the electromagnetic characteristics and homogenization of metasurface stacks but also explore the role of symmetry and geometry in the retrieved parameters. Additionally, our formulation paves the way toward a self-consistent design of metamaterials that emulate a desired scattering response.

We present an analytic approach to treat open quantum systems strongly coupled to multiple environments via noncommuting system operators: a prime example is a qubit concurrently coupled to both decohering and dissipative baths. Our approach, which accommodates strong system-bath couplings, generalizes the recently developed reaction-coordinate polaron transform method [N. Anto-Sztrikacs et al., PRX Quantum 4, 020307 (2023)] to handle couplings to baths via noncommuting system operators. Our approach creates an effective Hamiltonian that reveals the cooperative effect of the baths on the system. For a spin impurity coupled to both dissipative and decohering environments, the effective Hamiltonian predicts the suppression of relaxation by decoherence, a phenomenon previously observed in simulations but lacking so far a theoretical foundation. We also apply the method to an ensemble of spins coupled to local baths through noncommuting operators, demonstrating the engineering of the Kitaev XY spin chain interaction. Noncommutativity is a feature of quantum systems; future prospects of our approach include the study of thermal machines that leverage such genuine quantum effects.