The atomic structure of the most stable reconstructed surface of cuprous oxide $\left({\mathrm{Cu}}_2\mathrm{O}\right)\left(111\right)$ surface has been a longstanding topic of debate. In this study, we develop on-the-fly machine-learned force fields (MLFFs) to systematically investigate the various reconstructions of the ${\mathrm{Cu}}_2\mathrm{O}\left(111\right)$ surface under stoichiometric as well as O- and Cu-deficient or rich conditions, focusing on both $(\sqrt{3}\times \sqrt{3})\mathrm{R}{30}^{\circ }$ and $(2\times 2)$ supercells. By utilizing parallel tempering simulations supported by MLFFs, we confirm that the previously described nanopyramidal and Cu-deficient $(1\times 1)$ structures are the lowest energy structures from moderately to strongly oxidizing conditions. In addition, we identify two promising nanopyramidal reconstructions at highly reducing conditions, a stoichiometric one and a Cu-rich one. Surface energy calculations performed using spin-polarized PBE, $\text{PBE}+U$, ${\mathrm{r}}^2\mathrm{SCAN}$, and HSE06 functionals show that the previously known Cu-deficient configuration and nanopyramidal configurations are at the convex hull (and, thus, equilibrium structures) for all functionals, whereas the stability of the other structures depends on the functional and is therefore uncertain. Our findings demonstrate that on-the-fly trained MLFFs provide a simple, efficient, and rapid approach to explore the complex surface reconstructions commonly encountered in experimental studies, and also enhance our understanding of the stability of ${\mathrm{Cu}}_2\mathrm{O}\left(111\right)$ surfaces.

Bound states in the continuum (BICs), a universal wave phenomenon observed in plasmonic and other wave systems, remain spatially localized despite coexisting with a radiative continuum. However, current implementations of plasmonic BICs (pBICs) suffer from critical limitations: lack of dynamic tunability or poor stability in key parameters such as resonance wavelengths and quality factors (Q factors). In this paper, we propose a bilayer graphene metagrating with sinusoidal periodic conductivity modulation to address these challenges. We demonstrate two independent pBICs with quantized topological charge (−1, confirmed via momentum-space polarization singularities), emerging under in-phase and out-of-phase conductivity configurations. Remarkably, owing to the invariant coupling strength under arbitrary lateral offsets of interlayer conductivity patterns, these pBICs exhibit ultralow variance in both wavelengths and Q factors within a particular range of asymmetry parameters, ensuring unprecedented spectral stability under perturbations. The proposed metagrating architecture enables high-performance refractive index sensing and dual-mode perfect absorption, offering a robust platform for actively tunable pBIC devices with tailored spectral and topological functionalities.

We study a magnetic impurity placed in the two-dimensional antiferromagnetic quantum critical metal (AFQCM), using the field-theoretic functional renormalization group. Critical spin fluctuations represented by a bosonic field compete with itinerant electrons to couple with the impurity through the spin-spin interaction. At long distances, the antiferromagnetic electron-impurity (Kondo) coupling dominates over the boson-impurity coupling. However, the Kondo screening is weakened by the boson with increasing severity as the hot spots connected by the magnetic ordering wave vector are better nested. For $v_{0,i}\ll 1$, where $v_{0,i}$ is the bare nesting angle at the hot spots, the temperature $T_K^{\mathrm{AFQCM}}$ below which Kondo coupling becomes $O\left(1\right)$ is suppressed as $\frac{log\mathrm{\Lambda }/T_K^{\mathrm{AFQCM}}}{log\mathrm{\Lambda }/T_K^{\mathrm{FL}}}\sim \frac{g_{f,i}}{v_{0,i}log1/v_{0,i}}$, where $T_K^{\mathrm{FL}}$ is the Kondo temperature of the Fermi liquid with the same electronic density of states, and $g_{f,i}$ is the boson-impurity coupling defined at UV cutoff energy $\mathrm{\Lambda }$. The remarkable efficiency of the single collective field in hampering the screening of the impurity spin by the Fermi surface originates from ultraviolet/infrared (UV/IR) mixing: bosons with momenta up to a UV cutoff actively suppress Kondo screening at low energies.

The parity anomalous semimetal (PAS) phase is a topological state of matter exhibiting a semimetallic nature and a half-quantized Hall conductance of $e^2/h$ ($e$ is the elementary charge and $h$ is the Planck constant). In this work, we investigate the disorder-driven topological phase transition in a semimagnetic narrow-gap band insulator thin film. We demonstrate that strong disorder induces a transition from the narrow-gap band insulator to a PAS phase, accompanied by the emergence of a single gapless Dirac cone—the hallmark of the half-quantized Hall effect. Calculations of the local density of states reveal the spectral evolution underlying this transition, while finite-size scaling of the real-space Hall conductivity confirms the robustness of the half-quantized plateau over a finite range of disorder strengths. Our findings reveal disorder as a potent tool for engineering topological phases, in which the interplay between topology and localization in quantum materials warrants further exploration.

Surface plasmon resonances (SPRs) are crucial for confining light beyond the diffraction limit, yet metal losses often limit their spectral localization. Here, we propose a practical strategy for enabling the spectral localization of single-nanoparticle SPRs through photonic substrate engineering, which creates distinct optical pathways (OPs) to tailor the electromagnetic environments. By analyzing the multiplication factor spectrum of the projected local density of states, we can accurately trace these OPs, achieving high spatial and spectral localization of single-nanoparticle SPRs. Simulations show that using a photonic substrate can reduce the mode volume by a factor of 5 and enhance the quality factor by more than 80 times compared to a bare metal nanoparticle on a dielectric substrate. Subsequently, proof-of-concept experiments demonstrate the manipulation of single-nanoparticle SPRs by engineering OPs in both “open” and “closed” states, using two fabricated leaking Fabry-Pérot photonic substrates. This multidimensional photonic substrate engineering establishes a customizable platform for single-nanoparticle plasmonics, potentially transforming applications that were previously limited by spectral localization.

The lower mantle of Earth, characterized by pressures of 24–127 GPa and temperatures of 1900–2600 K, is still inaccessible to direct observations. In this work, we investigate by first principles the stability, phase diagram, elastic properties, and thermal conductivity of Davemaoite (${\mathrm{CaSiO}}_3$ perovskite), which constitutes a significant component of Earth's lower mantle. Notably, our simulations fully capture the anharmonic ionic fluctuations arising from the extreme temperatures and pressures of the lower mantle, thanks to stochastic self-consistent harmonic approximation. We show that the cubic phase of ${\mathrm{CaSiO}}_3$ is the ground state at the lower mantle's thermodynamic conditions. The phase boundary between the cubic and tetragonal phases increases linearly from 300 K to 1000 K between 12 and $100\mathrm{G}\mathrm{Pa}$. Accounting for temperature-renormalized phonon dispersions, we evaluate the speed of sound as a function of depth. Our results downplay the role of octahedral rotations on the transverse sound velocity of cubic ${\mathrm{CaSiO}}_3$, advocated in the past to explain discrepancies between theory and experiments. The lattice thermal conductivity, assessed thanks to the recently introduced Wigner formalism, shows a predominance of particle-like transport, thus justifying the standard Boltzmann transport approach even in a system with such strong ionic anharmonicity.

Ferroelectric high-entropy ceramics (HECs) have recently gained significant attentions in advancing high-performance energy storage and dielectric capacitors applications. A critical challenge is to understand the atomic-scale origin of their distinct macroscopic functionalities because HECs always have disordered atomic arrangements and complex lattice distortions. Here, through a combination of polarized Raman spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, and crystal orbital Hamilton population (COHP) calculations, we establish the routine to identify the multiscale physical process between phonon-bonding dynamics and lattice polarization responses in a HECs system, namely, $\left({\mathrm{Sr}}_{0.2}{\mathrm{Ba}}_{0.2}{\mathrm{Pb}}_{0.2}{\mathrm{La}}_{0.2}{\mathrm{Na}}_{0.2}\right){\mathrm{Nb}}_2{\mathrm{O}}_6$. We find that the off-centering Nb ions contribute to octahedral tilting. Specifically, the bending modes restrict O-Nb-O bond-angle distortions, strengthening the $ab$-plane covalent network to enhance breakdown fields. The rigid stretching mode suppresses oxygen displacement, thus stabilizing polar order. The constrained Nb vibration synergistically boosts maximum polarization via Nb-O bond stiffening and reduces remnant polarization. The COHP model theoretically compliments the experimental results. This work deciphers the multiscale interplay of structure-functionality relationship in HECs, offering a universal strategy to tailor high-entropy materials by multiscale analysis of phonon dynamics and bonding characteristics.

The Sachdev-Ye-Kitaev (SYK) model is of paramount importance for the understanding of both strange metals and a microscopic theory of two-dimensional gravity. We study the interplay between stabilizer Rényi entropy and entanglement entropy in both the ground state and highly excited states of the $\mathrm{SYK}-4+\mathrm{SYK}-2$ model, interpolating the highly chaotic four-body interactions model with the integrable two-body interactions one. The interplay between these quantities is also assessed through universal statistics of the entanglement spectrum and its antiflatness. We find that SYK-4 is indeed characterized by a complex pattern of both entanglement and nonstabilizer resources, while SYK-2 is nonuniversal and not complex. We discuss the fragility and robustness of these features depending on the interpolation parameter.

We have investigated the magnetic and transport properties of a unique combination of the topological Weyl ferromagnet (FM) ${\mathrm{Co}}_2\mathrm{MnGa}$ (CMG) and the topological insulator (TI) ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ (BT) in order to explore quantum materials and their heterostructures with nontrivial topology in real space as well as momentum space. The thickness- and temperature-dependent properties of this heterostructure are studied in detail. The interfacial perpendicular magnetic anisotropy is observed in ${\mathrm{Co}}_2\mathrm{MnGa}$ at a thickness as high as 3 nm. The thickness-dependent tuning of the Fermi level leads to distinct transport characteristics in CMG($t$)/BT heterostructures. The study also reports two unconventional observations in the Hall effect, i.e., the sign reversal of the anomalous Hall effect and the emergence of the topological Hall effect, both of which exhibit a significant dependence on temperature. The topological Hall effect, characterized by a high squareness ratio and a large Hall resistivity value of $\sim 189\mathrm{n}\mathrm{\Omega }\mathrm{cm}$ at 5 K, is observed in a wide temperature range below $T_c$ in the CMG(7 nm)/BT(10 nm) heterostructure. This effect can be attributed to the presence of chiral magnetic textures induced by the interfacial Dzyaloshinskii-Moriya interaction, arising from the strong spin-orbit coupling (SOC) of BT. This conclusion is supported by the absence of such unconventional signatures in transport and magnetic measurements in another similar series CMG($t$)/W(10 nm). Therefore, the interplay of strong intrinsic Berry curvature in CMG (as deduced from scaling mechanisms) and the high SOC of BT enable the FM/TI combination to host unconventional spin textures, which may provide an important building block for the next generation of spintronic devices.

Linear and nonlinear couplings of magnetic and lattice excitations are at the heart of many fascinating magnetophononic phenomena observed in rare-earth orthoferrites, the distinctive feature of which is the tendency to spin-reorientation transitions. Here we report the results of the experimental study of the spin and lattice dynamics in the Brillouin zone center of the rare-earth orthoferrite ${\mathrm{Sm}}_{0.55}{\mathrm{Tb}}_{0.45}{\mathrm{FeO}}_3$ by using polarized infrared reflectivity and Raman scattering spectroscopic techniques. The obtained results were supported by the first-principles calculations, which allowed us to reliably identify the parameters of most infrared- and Raman-active phonons. We reveal the spin-reorientation transitions ${\mathrm{\Gamma }}_4\left(G_a{F}_c\right)\stackrel{T_1}{\leftrightarrows }{\mathrm{\Gamma }}_{24}\left({\mathrm{G}}_{\mathrm{ac}}{\mathrm{F}}_{\mathrm{ac}}\right)\stackrel{T_2}{\leftrightarrows }{\mathrm{\Gamma }}_2\left({\mathrm{G}}_{\mathrm{c}}{\mathrm{F}}_{\mathrm{a}}\right)$ at $T_1\simeq 220\mathrm{K}$ and $T_2\simeq 130\mathrm{K}$ and carefully studied the following evolution of Raman scattering on magnetic excitations at these transitions. Notably, the intermediate magnetic structure ${\mathrm{\Gamma }}_{24}$ displays an exceptionally broad temperature range $\mathrm{\Delta }T=T_1-T_2\simeq 90\mathrm{K}$ in mixed ${\mathrm{Sm}}_{0.55}{\mathrm{Tb}}_{0.45}{\mathrm{FeO}}_3$ compared to pure rare-earth orthoferrites. We attribute this broadening of the intermediate phase to the modification of the magnetocrystalline anisotropy as a result of the inhomogeneous magnetic structure caused by the random distribution of rare-earth ${\mathrm{Sm}}^{3+}$ and ${\mathrm{Tb}}^{3+}$ ions. We found neither change in the parameters of Raman-active $B_{1g}$ phonons nor the appearance of new phonons induced by spin-reorientation transitions, which have been reported in ${\mathrm{SmFeO}}_3$. We assume that our results provide a solid basis for more deeper understanding of magnetophononic phenomena in rare-earth orthoferrites.

The coherence factors of quasiparticles in a superconductor determine their properties, including transport as well as their susceptibility to electric fields. In this work, we propose a way to infer the local coherence factors using local transport to normal leads. Our method is based on measuring the local current through a lead as the coupling to a second one is varied; the shape of the current is determined by the ratio between the local coherence factors, becoming independent of the coupling to the second lead in the presence of local electron-hole symmetry, i.e., coherence factors $\left|u\right|=\left|v\right|$. We apply our method to minimal Kitaev chains: arrays of quantum dots coupled via narrow superconducting segments. These chains feature Majorana-like quasiparticles (zero-energy states with $\left|u\right|=\left|v\right|$) at discrete points in parameter space. We demonstrate that the local current allows us to estimate the local Majorana polarization (MP)—a measurement of the local Majorana properties of the state. We derive an analytical expression for the MP in terms of local currents and benchmark it against numerical calculations for two- and three-sites chains that include a finite Zeeman field and electron-electron interactions. These results provide a way to quantitatively assess the quality of Majorana states in short Kitaev chains.

Materials with graphenelike layers attract tremendous attention due to their electronic structures and superconducting properties. In this study, we synthesized $\mathrm{La}{\mathrm{P}}_2$ polycrystalline and observed a superconducting transition at around 30 GPa. The critical temperature $T_c$ increases monotonically with pressure, which is nearing saturation and reaches 7.8 K at 78 GPa. The synchrotron x-ray diffraction experiments confirm the superconducting transition originates from a structure transition to the $P6\text{/}mmm$ phase under high pressure, suggesting the observation of graphenelike phosphorus layers in transition-metal phosphides. By first-principles calculations, we provide more evidence for the stability of the graphenelike phosphorus layers in $\mathrm{La}{\mathrm{P}}_2$. Our findings are helpful for the understanding of the $\mathrm{La}{\mathrm{P}}_2$ phase diagram under high pressure and could shed light on the research of unique structures in transition-metal phosphides under high pressure.

This paper explores the impact of Mn doping in the battery electrode material Li(Mn)${\mathrm{FePO}}_4$ by computational methods. Structures are generated at up to $6.25\%$ Li and $3.125\%$ Mn content with varying Li, Fe, and Mn configurations. The oxidation state of the Fe and Mn ions are explicitly set using occupation matrix control, while the structures are optimized using $\mathrm{DFT}+\mathrm{U}$. Although Mn is redox active and can exist in both the $+\mathrm{III}$ and $+\mathrm{II}$ states, there is a strong preference for the latter. We show that the charge-compensating electrons prefer to occupy the Mn sites rather than the Fe sites during Li insertion. This results in Mn(II) and Fe(II) ions that interact electrostatically with the positively charged Li ions. The $\mathrm{DFT}+\mathrm{U}$ data are consequently used to parametrize a Coulomb potential, incorporating short-range two-body corrections, and utilized within a Monte Carlo approach. The short-range order between the atomic species are then quantified by their coordination numbers at varying temperatures. The Monte Carlo sampling demonstrates lower Li-Li clustering in the Li(Mn)${\mathrm{FePO}}_4$ system at temperatures below 500 K and thus more disorder as compared to the undoped system. On average, this results in less cluster formation, which correlates with the enlarged solid solution region found in the ${\mathrm{LiMnFePO}}_4$ phase diagram.

Spin-gapped metals have recently emerged as promising candidates for spintronic and nanoelectronic applications, enabling functionalities such as sub-60 mV/dec switching, negative differential resistance, and nonlocal spin-valve effects in field-effect transistors. Realizing these functionalities, however, requires a deeper understanding of their magnetic behavior, which is governed by a subtle interplay between localized and itinerant magnetism. This interplay is particularly complex in spin-gapped metallic half-Heusler compounds, whose magnetic properties remain largely unexplored despite previous studies of their electronic structure. In this work, we systematically investigate the magnetic behavior of spin-gapped metallic half-Heusler compounds $XYZ$ ($X$ = Fe, Co, Ni, Rh, Ir, Pd, Pt; $Y$ = Ti, V, Zr, Hf, Nb, Ta; $Z$ = In, Sn, Sb), revealing clear trends. Co- and Ni-based compounds predominantly exhibit itinerant magnetism, whereas Ti-, V-, and Fe-based systems may host localized moments, itinerant moments, or a coexistence of both. To uncover the origin of magnetism, we apply the Stoner model, with the Stoner parameter $I$ estimated from Coulomb interaction parameters (Hubbard $U$ and Hund's exchange $J$) computed using the constrained random phase approximation (cRPA). Our analysis shows that compounds not satisfying the Stoner criterion tend to remain nonmagnetic. On the contrary, compounds that satisfy the Stoner criterion, generally exhibit magnetic ordering. highlighting the crucial role of electronic correlations and band structure effects in the emergence of magnetism. For compounds with magnetic ground states, we compute Heisenberg exchange parameters, estimate Curie temperatures ($T_{\mathrm{C}}$), and analyze spin-wave properties, including magnon dispersions and stiffness constants. These results provide microscopic insight into the magnetism of spin-gapped metallic half-Heuslers and establish a predictive framework for designing spintronic materials with tailored magnetic properties.

We study the $(q+1)$-state clock model on the simple cubic lattice by using Monte Carlo simulations. In addition to the nearest-neighbor coupling we consider a next-to-next-to-nearest-neighbor coupling. For a certain range of the parameters, the phase transition of the model shares the XY universality class. Leading corrections to scaling are studied by using finite-size scaling of dimensionless quantities, such as the Binder cumulant $U_4$. The spatial unisotropy, which causes subleading corrections, is studied by computing the exponential correlation length ${\xi }_{\text{exp}}$ in the high-temperature phase for different directions. In the case of the $q$-state clock model it turns out that by tuning the ratio of the two coupling constants, we can eliminate either leading or subleading corrections to scaling. These points on the critical line are close to each other. Hence in the improved model, where leading corrections to scaling vanish, also subleading corrections are small. By using a finite-size scaling analysis of our high statistics data we obtain $\eta =0.03816\left(2\right)$ and $y_t=1/\nu =1.48872\left(5\right)$ as estimates of the critical exponents.

Recent progress has enabled the controlled fabrication of domain walls (DWs) in graphene, which host topological kink states. Meanwhile, reliable techniques for constructing graphene-based Josephson junctions have been established. While the experimental prerequisites for combining DWs with Josephson junctions are now available, this direction remains largely unexplored. In this work, we theoretically investigate transport properties in graphene-based Josephson junctions mediated by topological kink states and propose three DW engineering strategies. (i) DW number engineering uncovers a continuous evolution of critical current interference pattern from Aharonov-Bohm oscillation to Fraunhofer diffraction with increasing DW number, reproducing experimental observations [J. Barrier et al., Nature (London) 628, 741 (2024)] and suggesting enhanced sensitivity for magnetometry applications. (ii) DW symmetry engineering demonstrates that an asymmetric configuration of DWs under magnetic field yields an ideal Josephson diode characterized by pronounced nonreciprocal transport. (iii) DW geometry engineering reveals that intersecting DWs enable controllable supercurrent splitting with ratios among leads tunable through the intersection angle, magnetic field, and superconducting phase difference. Our findings elucidate the rich physics of DW-based Josephson junctions and establish a versatile platform for next-generation quantum devices.

Recently observed signatures of Bose-Einstein condensation and superfluidity of dipolar excitons have drawn enormous attention to excitonic semiconductor bilayers. In superfluids, stabilization and observation of vortex matter is usually a decisive proof of coherent condensation order. However to date, the vortex behavior in a two-dimensional excitonic system with aligned dipolelike interactions that are long-range and everywhere repulsive has not been addressed. We provide a theoretical description of the vortex characteristics, interaction, and lattices in a dipolar exciton superfluid, solving the corresponding Gross-Pitaevskii equation, while varying the exciton dipole moments and the exciton density—both tunable in the experiment—by interlayer separation and gating, respectively. We draw particular attention to the appearance of a maximum in the density redistribution around the edge of each vortex, in the phase-space region where the dipole interactions are particularly strong, and where a transition to an incompressible exciton supersolid is expected.

We present detailed calculations for several significant properties of the kagome lattice in the presence of irradiation. We employ the Floquet-Magnus perturbation expansion to obtain the energy bands and the corresponding wave functions near the Dirac points for the kagome lattice in the presence of circularly or linearly polarized irradiation. In contrast with linearly polarized irradiation, for which the energy bands do not get modified, a band gap is opened up near the Dirac points, between the valence and conduction bands in the presence of circularly polarized irradiation. We calculated the exciton binding energy and the exciton energy for gapped kagome lattice as a function of the frequency and intensity of the irradiation. We compare the exciton binding energy and exciton energy in a monolayer with those in a double layer consisting of electrons in one layer and holes in a parallel layer, separated by an insulator to inhibit recombination. We predict that a phase transition in the kagome lattice from the semiconducting phase to the excitonic insulating phase can be induced by applying circularly polarized irradiation. We examine the conditions for such a phase transition. Superfluidity of dipolar excitons was investigated, as well as the collective properties of the kagome lattice by calculating the sum of ladder diagrams for the vertex, describing the dipole-dipole repulsion between excitons. We propose observation of Bose-Einstein condensation and superfluidity of quasi-two-dimensional dipolar excitons in two-layer kagome lattices in the presence of pumping by circularly polarized light. The energy spectrum of collective excitations and the sound velocity, as well as the effective mass of dipolar excitons, are obtained in the regime of pumping by circularly polarized light. The superfluid density $n_s$ and the temperature of the Kosterlitz-Thouless phase transition $T_c$ are shown to be monotonic increasing functions of the excitonic density $n$ and the interlayer separation $D$. We have also analyzed the dependence of superfluid density $n_s$ and the Kosterlitz-Thouless phase transition temperature on the parameters of circularly polarized light. We explore opportunities to tune exciton binding energy, the spectrum of collective excitations, and the critical temperature of superfluidity by applying circularly polarized irradiation.