Hydrogen-rich compounds that exhibit high-temperature superconductivity typically require extreme pressures, which severely limits their practical applicability. Recent theoretical predictions of the complex hydride ${\mathrm{Mg}}_2{\mathrm{IrH}}_6$ have introduced a new family of ${\mathit{M}}_2{\mathit{X}\mathrm{H}}_6$-type hydrides, highlighting the potential for high-temperature superconductivity at near-ambient pressure. Motivated by this, we have performed high-throughput first-principles investigations of the ${\mathit{M}}_2{\mathit{X}\mathrm{H}}_6$ family (M = IA, IIA, IIIA, IIB metals; X = B, C, N) to identify dynamically stable hydrides and explore their superconducting properties. Eleven boron-based hydrides, ${\mathit{M}}_2{\mathrm{BH}}_6$ (M = Li, Na, K, Rb, Cs, Ca, Sr, Ba, Sc, Y, La), featuring ${\mathrm{BH}}_6$ octahedral units have been identified. Notably, ${\mathrm{Li}}_2{\mathrm{BH}}_6$ is dynamically stable down to 16 GPa and exhibits a superconducting critical temperature of 121.25 K. Electronic structure and phonon analyses indicate that high-frequency hydrogen vibrations from strong B–H covalent bonding, reinforced by light Li atoms, dominate the electron–phonon coupling. In contrast, noble-metal-based ${\mathrm{Li}}_2{\mathit{X}\mathrm{H}}_6$ compounds (X = Cu, Ag, Au) exhibit distinct superconducting mechanisms, driven by $d$ electrons at the Fermi level and low-frequency metal vibrations. These findings expand the compositional space of the ${\mathit{M}}_2{\mathit{X}\mathrm{H}}_6$ family and highlight ${\mathrm{Li}}_2{\mathrm{BH}}_6$ as a promising candidate for near-ambient-pressure high-$T_c$ superconductivity.

The recent discovery of high-temperature superconductivity in the bilayer nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ has spurred intense interest in exploring analogous mechanisms in other transition metal oxides. This raises a pivotal question: can cuprates, as neighbors to nickelates in the periodic table, host similar two-orbital superconductivity? Here, we systematically investigate the electronic structure of a series of designed Ruddlesden-Popper cuprates. Our calculations reveal that the parent compound ${\mathrm{La}}_3{\mathrm{Cu}}_2{\mathrm{O}}_7$ is a weakly correlated metal, and hole doping fails to induce strong correlation. We find that the actual valence of the copper cations becomes strikingly pinned around $+2.3$, far away from the targeted $d^8$ configuration. This valence pinning is attributed to the in- herent charge-transfer nature of cuprates. We propose this mechanism as a general principle explaining the robust single-orbital physics consistently observed in the cuprate family, holding true even in materials like the high-$T_c$ superconductor ${\mathrm{Ba}}_2{\mathrm{CuO}}_{3+\delta }$ that appear structurally primed for two-orbital activity. Our results therefore conclude that the route towards two-orbital superconductivity is fundamentally obstructed in cuprates, providing a crucial constraint for the future design of high-temperature superconductors.

Symmetry analysis is a cornerstone of modern physics, with charge- and spacetime-orientation-reversal (CRT) symmetry being a subject of particular interest. Recent research has revealed that the CRT symmetry for fermions exhibits a fractionalization distinct from the ${\mathbb{Z}}_2^{\mathcal{C}}\times {\mathbb{Z}}_2^{\mathcal{R}}\times {\mathbb{Z}}_2^{\mathcal{T}}$ symmetry for scalar bosons. In fact, the CRT symmetry for fermions can be extended by internal symmetries such as fermion parity ${\mathbb{Z}}_2^F$, chiral symmetry ${\mathbb{Z}}_2^{\chi }$, and continuous symmetries, thereby forming a group extension of the aforementioned ${\mathbb{Z}}_2$ direct product, and suffices to rule out bilinear mass terms. In the conventional framework, a Majorana fermion is defined by a single Dirac fermion with trivial charge conjugation. However, this definition encounters a fundamental challenge when the spacetime dimension $d+1=5,6,7mod8$, where the real dimension of Majorana fermion (${\dim }_{\mathbb{R}}{\chi }_{\mathcal{C}\ell (d,0)}$) aligns with the real dimension of Dirac fermion (${\dim }_{\mathbb{R}}{\psi }_{\mathcal{C}\ell \left(d\right)}$), rather than being half as in other dimensions. This peculiarity necessitates the introduction of a symplectic Majorana fermion, defined by a pair of Dirac fermions with trivial charge conjugation, to account for the discrepancy. To include these two types of Majorana fermions, we embed the Majorana theory in $n_{\mathbb{R}}$ and define the Majorana fermion field as a representation of the real Clifford algebra, which exhibits an eightfold Bott periodicity. Within the Hamiltonian formalism, we identify the eightfold CRT-internal symmetry groups across general spatial dimensions. In the case of Dirac fermions, the fermion field is defined as a representation of the complex Clifford algebra, which has a twofold Bott periodicity. Interestingly, we discover that the CRT-internal symmetry groups exhibit an eightfold periodicity that is distinct from that of the complex Clifford algebra. In certain dimensions where distinct mass terms can span a mass manifold, the CRT-internal symmetries can act nontrivially upon this mass manifold. Employing domain wall reduction method, we are able to elucidate the relationships between symmetries across different dimensions.

We present an analysis of a square-lattice Harper-Hofstadter model with a periodically varying magnetic flux with time. By switching the dimensionless flux per plaquette between a set of values $\{p_j/q_j\}$ the Floquet quasienergy spectrum is folded into $Q=\mathrm{lcm}\left\{q_j\right\}$ bands. We determine closed-form analytical solutions for the quasienergy spectrum and Chern numbers for the $-1/2\to 1/2$ flux-switching case, as well as the Rudner-Lindner-Berg-Levin (RLBL) winding invariants $W$ numerically, and construct the corresponding topological phase diagram for arbitrary driving period. We find that generic flux-switching drives feature interlaced Hofstadter butterfly quasienergy spectra which may host Floquet topological phases with no static counterpart, and the gaps in the spectrum may be labeled according to a Diophantine equation which relates the quasienergy gap index to the fluxes attained in the drive and their associated per-step windings.

Type-II multiferroics offer a promising route to strong magnetoelectric coupling due to the magnetic-order-driven ferroelectricity. Most experimentally realized type-II multiferroics exhibit noncollinear magnetic order, whose complex interaction with external fields can impede the practical control of magnetoelectric effects. In contrast, type-II multiferroics with collinear magnetic order remain underexplored, with prior work largely limited to conventional antiferromagnets. In this work, using Landau theory and symmetry analysis, we investigate spin-order-induced ferroelectricity in collinear ferrimagnetic systems and derive the criteria in the minimal-case scenario. According to these criteria, we perform a rapid and efficient search and ultimately identify three promising ferrimagnetic multiferroic candidates from the Inorganic Crystal Structure Database (ICSD). Among them, the largest net magnetic moment per unit cell (u.c.) reaches 3.0 ${\mu }_B$, and the maximum polarization reaches 0.08 $\mu \mathrm{C}/{\mathrm{cm}}^2$, comparable to the typical multiferroics material ${\mathrm{TbMnO}}_3$. In addition, for the altermagnetic system, we searched for known magnetic structures in the MAGNDATA database and identified ${\mathrm{MnSe}}_2$ as a promising candidate material, exhibiting a polarization as high as 0.07 $\mu \mathrm{C}/{\mathrm{cm}}^2$. Notably, our results show that ferroelectric polarization behavior provides a clear criterion for distinguishing the two experimentally reported magnetic structures of ${\mathrm{MnSe}}_2$.

Uranium $5f$ electrons often yield heavy-fermion behavior via Kondo screening. However, the pronounced bad-metallic transport of uranium mononitride (UN) defies an incoherent Kondo explanation. Using density-functional theory combined with dynamical mean-field theory, we show that UN is a strongly correlated bad metal. The dominant correlations arise from intra-atomic Hund's exchange interaction between two $5f$ electrons, which aligns local magnetic moments and produces large quasiparticle mass renormalization. This identifies UN as a $5f$-electron analog of a Hund's metal—a paradigm chiefly associated with transition-metal $d$ systems. Our results motivate a reexamination of the interplay between Mott, Kondo, and Hund-driven correlations across actinide correlated materials.

We investigate fluctuation-dominated physics in a superconductor–insulator–superconductor Josephson junction modeled by a Bogoliubov–de Gennes Hamiltonian. The resulting free-energy functional, expanded in powers of the fluctuations, depends explicitly on the imbalance between the absolute values of the fluctuations in the two electrodes. By solving a Ginzburg-Landau equation for this imbalance field, we determine its spatial configuration and the corresponding Josephson current. Going beyond the harmonic approximation for the effective potential reveals the emergence of a regime characterized by singular behavior of the Josephson current.

We investigate the use of Berry curvature dipole in $n$-doped tellurium as a mechanism for achieving terahertz amplification and lasing by applying a DC electric field. When the electrical bias and wave vector are aligned along the trigonal $c$ axis, the right-handed circularly polarized mode experiences amplification at relatively low bias, while the left-handed mode is attenuated. Furthermore, when the electrical bias and wave vector are orthogonal to the $c$ axis, the structure supports elliptically polarized eigenmodes that also exhibit gain under suitable bias conditions, where the degree of ellipticity is tunable by the applied bias. We also investigate lasing conditions for a Fabry-Perot cavity incorporating biased Te as an active medium. Due to the resonance in the dielectric permittivity of tellurium, there are discrete lasing intervals. Our results show that bulk chiral tellurium could be used as an electrically tunable, polarization-selective gain medium for micrometer-scale terahertz lasers, with lasing achievable at bias fields below the material's breakdown threshold, paving the way towards new terahertz devices.

We investigate finite two-dimensional disordered systems with periodic confinement. At low energies, eigenstates exhibit strong Anderson localization, while at higher energies a subset of states exhibits variational scarring with anisotropic intensity patterns that deviate from random-wave expectations. Scaling theory predicts that in two dimensions all eigenstates localize in the large-system-size limit, yet the energy-dependent localization length and finite-size effects allow these regimes to coexist. We demonstrate that this coexistence produces distinct, robust signatures in both spatial intensity patterns and spectral statistics that are directly observable in mesoscopic electronic, photonic, and cold-atom systems.

The quantum anomalous Hall effect shows great promise for the realization of the ohm without the need for an external magnetic field. The most mature material platform is magnetically doped topological insulators. In these materials, precise quantization is limited to low temperatures, with the activation energy for dissipative transport typically in the range of $1\mathrm{K}$. One potential source of dissipative transport is nonchiral edge states. These states are expected to be present in sufficiently thick samples. In this work, we perform extensive Hall and nonlocal resistance measurements in a Hall bar geometry at 2 K. We perform 15 distinct measurements on a single device, each independent with respect to device symmetry and Onsager reciprocity. By comparing the results to different transport models, we find that the system behavior is well described by a simple continuum Ohm's law model. The addition of nonchiral edge states to the model does not significantly improve the fitting, and we conclude that there is not strong evidence for these states. We discuss the implications of our results for the prospect of a high-temperature quantized anomalous Hall effect in these materials.

We present an improved version of the algorithm contracting and optimizing finite projected entangled pair states (fPEPS) in conjunction with projected entangled pair operators (PEPOs). Our work has two components to it. First, we explain in detail the characteristic contraction patterns that occur in fPEPS calculations and how to slice them such that peak memory occupation remains minimal while ensuring efficient parallel computation. Second, we combine controlled bond expansion [A. Gleis, J.-W. Li, and J. von Delft, Phys. Rev. Lett. 130, 246402 (2023)] with randomized singular value decomposition [V. Rokhlin, A. Szlam, and M. Tygert, SIAM J. Matrix Anal. Appl. 31, 1100 (2009)] and apply it throughout the fPEPS algorithm. We present benchmark results for the Hubbard model for system sizes up to $8\times 8$ and SU(2) symmetric bond dimension of up to $D=6$ for PEPS bonds and $\chi =500$ for the environment bonds. Finally, we comment on the state and future of the fPEPS-PEPO framework.

Recently, the first successful synthesis of bulk manganese monocarbide (MnC) has been reported. The compound crystallizes in the zinc-blende structure and has been proposed as a potential superhard material. In this work, we present a comprehensive first-principles study of the structural, electronic, and magnetic properties of MnC using several exchange-correlation approximations. We demonstrate that the SCAN meta-GGA (generalized gradient approximation)  and the Perdew-Burke-Ernzerhof zero revised (PBE0r) hybrid functional outperform GGA–Perdew-Burke-Ernzerhof for solids (PBEsol), Heyd-Scuseria-Ernzerhof 2006 (HSE06), and the mean-field density functional theory [($\mathrm{DFT}\left)\right]+U+V$ schemes in correctly predicting the experimentally observed zinc-blende structure as the ground state. Our analysis reveals that the bond-exchange interaction plays a decisive role in stabilizing this phase. At theoretical equilibrium, hybrid functionals (PBE0r and HSE06) predict a metallic ground state, whereas semilocal functionals (PBEsol and SCAN) and $\mathrm{DFT}+U+V$ yield two distinct types of half-metallic ferromagnetism with opposite volume dependence, opening a debate on the origin and nature of this behavior. If confirmed experimentally, such a property would make MnC an attractive candidate for spintronic applications.

We introduce two classes of junctions in a toric code, a prototypical model of a ${\mathbb{Z}}_2$ quantum spin liquid, and study the nature of anyonic transport across them mediated by Zeeman fields. In the first class of junctions, termed potential barrier junctions, the charges sense effective static potentials and a change in the band mass. In a particular realization, while the junction is completely transparent to the electric charge, magnetic charge transmission is allowed only after a critical field strength. In the second class of junctions, we stitch two toric codes with operators which do not commute at the junction. We show that the anyonic transmission gets tuned by effective pseudospin fluctuations at the junction. Using exact analytical mappings and numerical simulations, we compute charge-specific transmission probabilities. Our work, apart from uncovering the rich physical mechanisms at play in such junctions, can motivate experimental work to engineer defect structures in topologically ordered systems for tunable transport of anyonic particles.

The Kondo effect is a hallmark of strongly correlated systems, where an impurity's local degrees of freedom are screened by conduction electrons, forming a many-body singlet. With increasing degrees of freedom in the impurity, theoretical studies face significant challenges in accurately identifying and characterizing the underlying mechanisms that screen the impurity. In this work, we introduce a straightforward yet powerful methodology for identifying the formation of Kondo singlets and their screening mechanisms, by utilizing the numerical renormalization group combined with the matrix product states technique. We demonstrate the effectiveness of our method on the single and two-level Anderson impurity models. Furthermore, we outline generalizations to multichannel and multiorbital Kondo impurities, showing how advanced tensor network techniques render our approach a versatile framework for tackling complex impurity systems.

Indium phosphide (InP) has attracted significant interest in high-frequency electronics, optoelectronics, and photovoltaics due to its wide band gap, high electron saturation velocity, and superior electron mobility. However, its relatively low hole mobility remains a pivotal bottleneck for practical applications. This study, employing mode-level first-principles calculations, elucidates that interband electron-phonon scattering is the primary factor limiting hole mobility in InP. Our results show that uniaxial strain induces splitting of the light-hole ($lh$) and heavy-hole ($hh$) bands near the valence band maximum. This splitting significantly suppresses the $lh-hh$ interband scattering, thereby substantially enhancing hole mobility. Furthermore, tailored uniaxial strain can enhance electron mobility by reducing scattering rates near the conduction band minimum. Specifically, our predictions indicate that hole mobility in InP along the [100] and [001] directions increases by approximately $240\%$ and $88\%$, respectively, under uniaxial compressive strain of $4\%$. These findings uncover a carrier transport mechanism and provide a generalized strategy for enhancing hole mobility in zinc-blende semiconductors.

Type-II hyperbolic lattices constitute a new class of hyperbolic structures that are projected onto the Poincaré ring and possess both an inner and an outer boundary. In this work we reveal the higher-order topological phases in type-II hyperbolic lattices, characterized by the generalized quadrupole moment. Unlike the type-I hyperbolic lattices where zero-energy cornerlike states exist on a single boundary, the higher-order topological phases in type-II hyperbolic lattices possess zero-energy cornerlike states localized on both the inner and outer boundaries. These findings are verified within both the modified Bernevig-Hughes-Zhang model and the Benalcazar-Bernevig-Hughes model. Furthermore, we demonstrate that the higher-order topological phase remains robust against weak disorder in type-II hyperbolic lattices. Our work provides a route for realizing and controlling higher-order topological states in type-II hyperbolic lattices.

Single atomic wires of transition metal compounds have been successfully isolated within carbon nanotubes. These real one-dimensional (1D) materials with enhanced electron-electron correlations and strong electron-phonon coupling provide a unique platform to explore the competition and synergy among different quantum phases. Here we predict a new single atomic wire of niobium triiodide (${\mathrm{NbI}}_3$). Under the ${\mathrm{D}}_{2\mathrm{h}}$ symmetry, pronounced states from localized Nb-$d$ orbitals emerge at the Fermi level, inducing strong electron correlations and instability. Inclusion of Hubbard $U$ leads to a metal-to-insulator transition. Simultaneous Peierls dimerization occurs and coexists with the Mott state. Consistently, our first-principles calculations identify a ground state with ${\mathrm{C}}_{2\mathrm{v}}$ symmetry in ${\mathrm{NbI}}_3$ atomic wire and antiferromagnetic order featuring strong magnetic anisotropy. Notably, the bands near the gap remain nearly flat with narrow bandwidths irrespective of the $U$ value, indicating strongly suppressed electron kinetic energy. These results shed light in exploring correlated physics in single atomic wires and pave the way for quantum devices governed by the interplay between spin and charge orders.

$T_d$ phase type-II Weyl semimetals are of technological interest in part due to their novel sliding ferroelectricity and nontrivial topology being dependent on their van der Waals stacking orders. Optical manipulation of these stacking orders via interlayer sliding can lead to new types of energy-efficient ultrafast memory and topological switches. Despite the existing reports on $T_d$ phase $\mathrm{WT}{\mathrm{e}}_2$ and $\mathrm{MoT}{\mathrm{e}}_2$, such light-driven sliding dynamics are unexplored in ternary $\mathrm{TaIr}{\mathrm{Te}}_4$, a material that has recently demonstrated more pronounced topological properties and greater environmental stability. Here we apply an ultrafast near-infrared pulse to bulk $\mathrm{TaIr}{\mathrm{Te}}_4$ and observe a $15\text{−}\mathrm{c}{\mathrm{m}}^{-1}$ coherent interlayer shear phonon in both transient reflectivity and time-resolved second harmonic generation (TRSHG). The initial cosinelike phase of this oscillation is characteristic of a displacive excitation mechanism, evidencing a pump-induced excited state distortion along the interlayer sliding coordinate. With increasing pump fluence, the temporal phase of the oscillation undergoes a π phase shift. We exclude a sliding ferroelectric switching origin using phase-sensitive TRSHG, instead concluding that the coherent phonon phase shift arises from inversion of the sliding distortion direction, supported by first-principles calculations of the crystal polarization. Our findings advance the understanding of nonequilibrium properties in layered topological semimetals and may serve as proof of principle for ultrafast electronics based on terahertz-speed modulation of the symmetry-dependent topological properties of $\mathrm{TaIr}{\mathrm{Te}}_4$.

We numerically study topological effects of electromagnetic (EM) waves in a two-dimensional non-Hermitian photonic crystal composed of lossy magneto-optical materials. In this system, not only the EM wave functions but also the complex eigenfrequencies exhibit nontrivial topological properties. We demonstrate that the non-Hermitian skin effect, protected by point gaps in the complex eigenfrequency spectrum, emerges at both the edges and corners of truncated structures. This phenomenon has no counterpart in Hermitian systems. In addition, we identify non-Hermitian topological edge states originating from the nontrivial topology of the bulk bands. While most previous studies of non-Hermitian topology have focused on tight-binding models, our work addresses a continuous photonic system, providing a more realistic platform and offering a concrete route toward experimental realization of non-Hermitian effects.

The spin-dependent transport properties and spin polarization through a time-periodic potential well in the altermagnet are investigated. Photon-assisted transport occurs in periodically driven quantum systems, where incident electrons can exchange energy with the driven field by absorbing or emitting photons (in units of $\hslash \omega$), leading to transitions between electron channels. The photon-assisted tunneling spectrum in the altermagnet features Fano resonances with asymmetric line shapes, where the resonance energy is located exactly at $E=E_b+\hslash \omega$ ($E_b$ is the bound-state energy in the static potential). The transport is spin-polarized and depends sensitively on the orientation of the altermagnet relative to the interface. Compared with conventional ferromagnetic and antiferromagnetic mechanisms, the transmission in our system presents alternating zero or nonzero net magnetization. These orientation-dependent transport characteristics highlight the unique nature of the altermagnetic state.