Parity-time-reversal symmetric ($\mathcal{PT}$-symmetric) magnets have garnered much attention due to their spin-charge coupled dynamics enriched by parity-symmetry breaking. By real-time simulations, we study how localized spin dynamics can affect the nonlinear Hall effect in $\mathcal{PT}$-symmetric magnets. To identify the leading-order term, we derive analytical expressions for the second-order optical response and classify the contributions by considering their transformation properties under $\mathcal{PT}$ symmetry. Notably, our results reveal that sizable contribution is attributed to the mixed dipole effect, which is analogous to the Berry curvature dipole term.

The magnetic property of Heusler alloys can be predicted by the famous Slater-Pauling (S-P) rule, which states that the total magnetic moment $\left(m_t\right)$ of such materials can be expressed as $m_t=(N_V-24){\mu }_B/\text{f.u.}$, where $N_V$ is the total valence electron count (VEC). Consequently, no Heusler alloys having VEC = 24 are theoretically expected, as well as experimentally reported, to have any magnetic ordering. Recently, a special class of Heusler alloys with 50% concentration of $p$-block elements (anti-Heusler) have been identified, although none such reported compounds belong to the VEC 24 category. Here, we report an anti-Heusler alloy, ${\mathrm{Al}}_2\mathrm{MnCu}$, that undergoes long-range ferromagnetic ordering with $T_{\mathrm{C}}\sim 315$ K and a large magnetic moment of $\sim 1.8{\mu }_B/\mathrm{f}.\mathrm{u}.$ despite having VEC 24. A phenomenological model based on molecular orbital hybridization is also proposed to understand the magnetism and unusual deviation from the standard S-P rule.

The superconducting diode effect (SDE), the nonreciprocity of the critical current in a bulk superconductor, has garnered significant attention due to its potential applications in superconducting electronics. However, the role of disorder scattering in SDE has rarely been considered, despite its potential qualitative impact, as we demonstrate in this work. We investigate SDE in a disordered Rashba superconductor under an in-plane magnetic field, employing a self-consistent Born approximation to derive the corresponding Ginzburg-Landau theory. Our analysis reveals two surprising effects. First, in the weak Rashba spin-orbit coupling (SOC) regime, disorder can reverse the direction of the diode effect, indicated by a sign change in the superconducting diode efficiency coefficient. Second, in the strong Rashba SOC regime, disorder becomes the driving mechanism of SDE, which vanishes in its absence. In this case, we show that disorder-induced mixing of singlet and triplet superconducting orders underlies the effect.

We study the diode effect of the supercurrent in the Josephson junctions with the loop current states as the tunneling barrier. The loop current states are realized by the Haldane model, which preserves the inversion symmetry and thus forbids the diode effect. We demonstrate how the inversion symmetry can be broken in the monolayer and bilayer systems. In the monolayer system, inversion symmetry can be broken by either introducing a sublattice staggered potential for the Haldane model or introducing a modified Haldane model, and in the bilayer system, it can be broken by either staking the two layers with opposite current directions or by directly applying an electric field perpendicular to the layers. We further show that the diode efficiency can be tuned by the interlayer coupling and the strength of the electric field or interlayer voltage. Our results provide another route to realize the Josephson diode effect by breaking the time-reversal symmetry through the loop current states.

Weyl semimetals have a variety of intriguing physical properties, including topologically protected electronic states that coexist with conducting states. Possible exploitation of topologically protected states in a conducting material is promising for technological applications. Weyl semimetals that form in a noncentrosymmetric structure that also contain magnetic moments may host a variety of emergent phenomena that cannot be seen in magnetic, centrosymmetric Weyl materials. It can be difficult to distinguish definitively between a centrosymmetric structure and one of its noncentrosymmetric subgroups with standard powder x-ray diffractometers in cases where two atoms in the compound have nearly the same atomic number, as is the case for the candidate Weyl semimetal CeGaGe. In these cases, a careful single-crystal neutron diffraction experiment with high-angle reflections provides complimentary information to x-ray diffraction and definitively resolves any ambiguity between centrosymmetric and noncentrosymmetric crystal structures. Single-crystal neutron diffraction measurements on the candidate Weyl semimetal CeGaGe confirms that its structure is noncentrosymmetric, described by space group 109 $\left(I{4}_{1}md\right)$ rather than the centrosymmetric space group 141 $(I{4}_1/amd)$. There are many high-angle reflections in the dataset that give clear, physically intuitive evidence that CeGaGe forms with $I{4}_{1}md$ symmetry since Bragg planes of these reflections can contain Ga with no Ge or vice versa, whereas the Bragg planes for a structure with $I{4}_1/amd$ symmetry would have a mix of Ga and Ge. Further, in some crystals we have studied, there is clear evidence for a structural transition from body-centered $I{4}_{1}md$ symmetry to primitive $P{4}_3$ and/or $P{4}_1$ symmetry.

Pressure tuning has emerged as a powerful strategy for manipulating the thermoelectric properties of materials by inducing structural and electronic modifications. Herein, we systematically investigate the transport properties and thermoelectric performance concerning lattice distortions induced by hydrostatic pressure in Ag-based chalcopyrite $\mathrm{Ag}X{\mathrm{Te}}_2$ $(X=\mathrm{In}, \mathrm{Ga})$. Our findings reveal that the lattice distortion in $\mathrm{Ag}X{\mathrm{Te}}_2$ exhibits distinct behaviors under lattice compression, diverging from trends observed at ambient pressure. Importantly, the hydrostatic pressure breaks the phenomenally negative correlation between thermal conductivity and lattice distortion. Pressure-induced softening of low-frequency acoustic phonons broadens the low-energy phonon spectrum, enhancing interactions between acoustic and optical phonons. Such broadening substantially increases the number of available three-phonon scattering channels, resulting in a marked reduction in thermal conductivity. Additionally, the applied pressure achieves a notable net increase in the power factor despite the strong coupling of electrical transport parameters, which underscores the potential for bidirectional optimization of transport properties in $\mathrm{Ag}X{\mathrm{Te}}_2$. As a result, the maximum ZT value of ${\mathrm{AgInTe}}_2$ is nearly doubled, demonstrating that pressure modulation is a powerful strategy for enhancing thermoelectric performance. Our work not only establishes the link between pressure, lattice dynamics, and thermoelectric properties within chalcopyrite $\mathrm{Ag}X{\mathrm{Te}}_2$, but also inspires the exploration of pressure-related optimization strategies for conventional thermoelectric materials.

Metal borides (MBs) have recently sparked enormous interest owing to their fascinating structures, superior properties, and widespread applications, including superconductivity. However, metal-bearing borides featuring both interstitial anionic electrons (IAEs) and superconductivity, remain scarce. Here, leveraging comprehensive first-principles structure prediction, we identified several abnormal stoichiometric aluminum-boron phases induced by compression, i.e., stable phases $\mathrm{A}{\mathrm{l}}_3{\mathrm{B}}_2$ and ${\mathrm{AlB}}_4$ and metastable phases AlB and ${\mathrm{AlB}}_6$. Strikingly, unlike other binary MBs, the unexpected coexistence of zero-dimensional IAEs located at the center of an $\mathrm{A}{\mathrm{l}}_6$ octahedron and superconductivity is uncovered in compressed $\mathrm{A}{\mathrm{l}}_3{\mathrm{B}}_2$ with a B dimer, and the IAEs experience a rare presence-to-disappearance transition during decompression. Electron-phonon coupling (EPC) simulations demonstrate that both Al intercalation compounds ${\mathrm{AlB}}_4$ with bilayer boron and ${\mathrm{AlB}}_6$ with trilayer boron have higher superconducting critical temperatures ($T_c=9.9$ K for ${\mathrm{AlB}}_4$, 7.2 K for ${\mathrm{AlB}}_6$) than 5.6 K for $\mathrm{A}{\mathrm{l}}_3{\mathrm{B}}_2$ at 1 atm, which is primarily attributed to the strong coupling between the B $2p$ electron states at the Fermi level and the high-frequency B-associated phonon modes. Remarkably, the $T_c$ of ambient-pressure ${\mathrm{AlB}}_4$ can be further improved to 28.7 K by an electron doping strategy that induces significant phonon modes softening and further enhances the EPC strength. In this paper, we provide a fresh perspective for MBs and point the way to the discovery of emerging boron-based materials containing metals.

We present a single-crystal Cu nuclear magnetic resonance (NMR) study of the cuprate superconductor ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ with hole-doping levels between $x=2$ and 8%. Measurements with short spin echo times enable us to systematically study the local properties of the electronic spin system in the region of the phase diagram where the material evolves from the insulating antiferromagnetic parent phase to the superconducting state. We find evidence for qualitative changes as the Sr concentration increases through $x=5$% in both NMR spectra and relaxation times, which we interpret as signatures of a low-temperature transition from a state with disconnected metallic islands to a granular metal with tunneling between the grains. These results provide microscopic insight into the physics of a doped charge-transfer insulator in the presence of quenched substitutional disorder, indicate that a connectivity transition occurs, and demonstrate that complex nanoscale electronic phase separation is ubiquitous in LSCO around the doping level where superconductivity first appears in the phase diagram.

Collective charge excitations directly probed in electron energy loss and inelastic x-ray scattering spectroscopies play a key role in different fields of condensed matter physics. Being induced by the long-range part of the Coulomb interaction between particles, in standard bulk systems they appear as well-defined features in the spectra associated with the zero crossing of the real part of the macroscopic dielectric function. However, this simple criterion cannot be used to identify collective excitations in low-dimensional systems where the macroscopic dielectric function is not a well-defined concept. In this work, we discuss how this problem can be traced back to the definition of the long-range Coulomb interaction, and we show how appropriate separation between long- and short-range Coulomb interactions allows one to correctly express the low-dimensional macroscopic dielectric function in terms of microscopic quantities accessible in first-principles calculations. This allows disentangling collective charge excitations in low-dimensional materials in analogy with what one does in standard bulk systems. In addition, we show how important macroscopic quantities, such as the screening length scale, can be extracted from full first-principle calculations. As an illustrative example we study the screening effects and the collective excitations in prototypical two-dimensional materials, including metals (${\mathrm{NbSe}}_2$) and semiconductors (BN and ${\mathrm{MoS}}_2$).

Experimental studies on pressure-induced phase transitions of realgar have been controversial, with experimental results from three different research groups showing that realgar exhibits different types of phase transition behavior at pressures below 20 GPa. Due to the important role of van der Waals force in molecular crystal systems, the vibration properties and Hirshfeld fingerprints of $\alpha \text{−}\mathrm{A}{\mathrm{s}}_4{\mathrm{S}}_4$ under different pressures are calculated by using a dispersion-corrected density functional theory method. Based on the calculated results of phonon spectra and Raman vibrational modes, the pressure-induced phase transition behavior of realgar is confirmed as isostructural phase transition. This phase transition type of realgar is further verified by the analysis of intermolecular forces given by the Hirshfeld fingerprints. Meanwhile, the calculations of the hole effective mass for realgar, solid nitrogen, and ethane show that the effective mass has considerable potential to judge phase transition. The effective mass indicates that the isostructural phase transition of realgar occurs at 8 GPa. This result is closer to the experimental phase transition pressure than the phase transition point given by the vibrational properties.

Rhenium diselenide (${\mathrm{ReSe}}_2$) presents pronounced lattice anisotropy and relatively weak interlayer interactions, which can result in its superior compressibility under pressure, as compared to other two-dimensional (2D) transition metal dichalcogenides (TMDs). Here, we employed diamond anvil cells (DAC) to apply stress fields up to 15.90 GPa, unveiling the intricate relationships among layer numbers, anisotropic properties, and specific structural variations in ${\mathrm{ReSe}}_2$. A rapid decrease in the anisotropic parameter $\sigma$ from the $E_g$-like modes can be observed at 6–8 GPa. It was found that the layers (3, 10, and 17 L) could be correlated with the ratio of the $ab$-plane to $c$-axis components ($I_{ab}/I_c$), ultimately identifying the anisotropic structural deformation as either hydrostatic strain or uniaxial strain. Moreover, the pressure-dependent band gap analysis elucidated the interlayer interactions along the $c$ axis. The present findings deepen understanding of ${\mathrm{ReSe}}_2$'s structural response to stress field and facilitating advancements in strain-based device applications.

Predictions of topological $p$-wave superconductivity and Majorana zero modes (MZMs) in hybrid superconductor-semiconductor nanowires have been difficult to realize experimentally. Consequently, researchers are actively exploring alternative platforms for MZMs. In this work, we theoretically study depleted nanowires with intrinsic superconductivity (as opposed to proximity-induced). Using a self-consistent Hartree-Fock-Bogoliubov mean field theory, we compute the topological phase diagram versus Zeeman field and filling for intrinsic wires with attractive interactions. We find that, although intrinsic wires could be less vulnerable than hybrids to topology-adverse effects, such as disorder and metallization, they are hindered by a fundamental limitation of their own. Although a topological $p$-wave gap is indeed possible, it is far less robust than in hybrid Majorana nanowires. Instead of remaining stable beyond the topological transition, it is found to decay exponentially with Zeeman field, greatly reducing the parameter region with an appreciable topological gap.

We investigate the anisotropic behaviors in PbTe and PbTe-Pb hybrid nanowires. In previous studies on PbTe, wire-to-wire variations in anisotropy indicate significant device disorder, posing a serious challenge for applications. Here, we achieve reproducible anisotropy in PbTe nanowires through a substantial reduction of disorder. We then couple PbTe to a superconductor Pb, and observe a pronounced deviation in the anisotropy behavior compared to bare PbTe nanowires. This deviation is gate tunable and attributed to the spin-orbit interaction and orbital effect, controlled by charge transfer between Pb and PbTe. These results provide guidance for the controlled engineering of exotic quantum states in this hybrid material platform.

Controlling the nature of coexisting multiple Fermi surfaces through their interplay is crucial for uncovering exotic superconducting phenomenology. Among high-temperature superconductors, ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-x}$ (YBCO) is notable for hosting a two-dimensional ${\mathrm{CuO}}_2$ plane and one-dimensional CuO chain Fermi surfaces. However, tuning the oxygen concentration alone has proven insufficient to induce significant hybridization between them. Here, we investigate the electronic states of Ca-doped YBCO epitaxial thin films using in situ angle-resolved photoemission spectroscopy. Ca doping, in combination with the induced oxygen deficiency and surface anomaly, enables significant electron filling imbalance between the planes and chains. Remarkably, this results in a substantial momentum-space overlap of their respective multiple Fermi surfaces. Our findings in Ca-YBCO films offer a pathway for exploring unconventional superconductivity beyond the conventional $d$-wave paradigm, using surfaces and interfaces as a platform.

Compounds of the materials class $LnT{\mathrm{Al}}_4{X}_2$ ($Ln$ = lanthanide, $X$ = tetrel, $T$ = transition metal) host exotic magnetic phenomena due to geometric frustration induced by their triangular lattice. Complex spin arrangements, magnetic fluctuations, and double magnetic transitions have been well observed by means of magnetotransport. Nevertheless, the experimental electronic structure of this family of materials has been poorly studied. We have investigated the experimental electronic structure of two members of this class of materials: ${\mathrm{SmAuAl}}_4{\mathrm{Ge}}_2$ and ${\mathrm{TbAuAl}}_4{\mathrm{Ge}}_2$. By means of angle-resolved photoemission spectroscopy (ARPES) accompanied by density functional theory calculations, we reveal common trends and features, the important effect of localized spin moments on the electronic structure, the presence of surface-localized electronic states, and the nature of the surface termination layer. Low-dimensionality, exchange interaction, and spin-orbit coupling are all important ingredients of the electronic structure.