Understanding the microscopic origin of intrinsically low lattice thermal conductivity is crucial for the design of thermoelectric materials. Here, the lattice dynamics and thermal transport of layered $X\mathrm{Ag}Y (X=\mathrm{K},\mathrm{Rb},\mathrm{Cs};Y=\mathrm{S},\mathrm{Se},\mathrm{Te})$ compounds with the P4/nmm structure are investigated using first-principles calculations by explicitly accounting for high-order anharmonicity and phonon coherence. All $X\mathrm{Ag}Y$ compounds exhibit remarkably low lattice thermal conductivity, with ${\kappa }_L$ at 300 K confined to a narrow range of approximately 0.334–$0.643\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$, reaching as low as $0.334\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ in CsAgTe. The strong suppression of the incoherent (Peierls-type) contribution originates from pronounced quartic anharmonicity and enhanced four-phonon Umklapp scattering, which can be traced to the distorted Ag–Y tetrahedral environment and the associated nonuniform distribution of bonding rigidity, giving rise to an anomalously strong bond–strong anharmonicity coupling. Beyond the phonon gas model, coherent phonon transport becomes non-negligible at elevated temperatures, particularly along the $c$ axis, arising from strong inter-branch coupling among high-frequency optical phonons that enables wave-assisted energy transfer. These results reveal a cooperative mechanism combining high-order anharmonicity and phonon coherence, providing a transport paradigm beyond the Peierls picture for intrinsically low-${\kappa }_L$ layered materials.

All-$d$ Heusler alloys are promising candidates for advanced spintronic and magnetoelastic applications, yet many lack the intrinsic large anomalous Hall conductivity (AHC) and magnetostriction required for practical device integration. In this work, we systematically investigate the topological transport and magnetostrictive properties of 81 heavy-element substituted Co-based all-$d$ Heusler alloys ${\mathrm{Co}}_{2}YZ\left(R\right)$ $(Y=\mathrm{Cr},\mathrm{Mn},\mathrm{Fe};Z=\mathrm{Sc},\mathrm{Ti},\mathrm{V}; \text{and} R=\mathrm{Re},\mathrm{Os},\mathrm{Ir},\mathrm{Pt})$ using first-principles calculations. We demonstrate that the fractional substitution of $5d$ transition metals serves as a highly effective strategy to tune the electronic structure via strong spin-orbit coupling (SOC). Our calculations identify eight materials exhibiting giant AHC values exceeding 1000 S/cm, with ${\mathrm{Co}}_2{\mathrm{Mn}}_{0.75}{\mathrm{Os}}_{0.25}\mathrm{Sc}$ and ${\mathrm{Co}}_2{\mathrm{Mn}}_{0.75}{\mathrm{Re}}_{0.25}\mathrm{V}$ approaching 1500 S/cm. Detailed symmetry and electronic structure analyses reveal that this massive AHC originates from the SOC-induced gap opening of Weyl nodal lines near the Fermi level, which generates an extended distribution of large Berry curvature. Furthermore, the introduction of strong SOC significantly enhances the magnetocrystalline anisotropy energy, transforming alloys with initially negligible magnetostriction into high-performance magnetoelastic materials. Notably, ${\mathrm{Co}}_2{\mathrm{Fe}}_{0.75}{\mathrm{Os}}_{0.25}\mathrm{Ti}$ and ${\mathrm{Co}}_2{\mathrm{FeSc}}_{0.75}{\mathrm{Ir}}_{0.25}$ exhibit giant magnetostriction coefficients of 752 and 609 ppm, respectively. Our findings establish heavy-element substitution as a robust, dual-purpose approach for the design and realization of multifunctional topological magnetic materials.

The development of room-temperature magnetic semiconductors is critical for advancing spintronic technologies, yet van der Waals magnets like ${\mathrm{CrI}}_3$ exhibit intrinsically low Curie temperatures ($T{}_{\mathrm{C}} \sim 45$ K). This study employs first-principles calculations to demonstrate that atom intercalation, particularly lithium (Li), dramatically enhances magnetic-exchange couplings in ${\mathrm{CrI}}_3$, achieving near-room-temperature ferromagnetism with a predicted $T{}_{\mathrm{C}}$ of 286 K, aligning with experimental reports of 420 K. The underlying mechanism involves synergistic superexchange and double-exchange interactions: intercalation reduces the $|E_p-E_d|$ energy difference between iodine p-orbitals and chromium $d$ orbitals, strengthening superexchange pathways, while charge transfer induces valence mixing (e.g., ${\mathrm{Cr}}^{3+}$ to ${\mathrm{Cr}}^{2+}$, as confirmed by experimental x-ray photoelectron spectrometry data), promoting double exchange. Theoretical predictions extend to other intercalants including Cu and Na, with ${\mathrm{Cu}}_{0.25}{\mathrm{CrI}}_3$ and ${\mathrm{Na}}_{0.25}{\mathrm{CrI}}_3$ exhibiting $T{}_{\mathrm{C}}$ of 267 K and 247 K, respectively, establishing a versatile strategy for designing high-$T{}_{\mathrm{C}}$ magnetic semiconductors. This work bridges theoretical insights and experimental validation, offering a transferable framework for intercalation-driven material design and accelerating practical spintronic device realization.

Lithium-abundant electrides, characterized by the presence of interstitial anionic electrons, have attracted considerable attention owing to their extraordinary properties, including superconductivity. Here, we conduct comprehensive first-principles structure-prediction simulations to investigate the phase stability of lithium-platinum (Li-Pt) compounds under high-pressure conditions. Our calculations identify several hitherto unknown electride phases in the Li-Pt system, namely, $\mathrm{L}{\mathrm{i}}_4\mathrm{Pt}, \mathrm{L}{\mathrm{i}}_5\mathrm{Pt}, {\mathrm{Li}}_6\mathrm{Pt}, {\mathrm{Li}}_{11}\mathrm{Pt}$, and $\mathrm{L}{\mathrm{i}}_{12}\mathrm{Pt}$. Among the metallic phases uncovered, ${\mathrm{Li}}_6\mathrm{Pt}$ exhibits the highest superconducting critical temperature ($T_{\mathrm{c}}$), reaching 18 K at 120 GPa. Strikingly, $\mathrm{L}{\mathrm{i}}_{12}\mathrm{Pt}$, the phase with the highest lithium content, is unexpectedly predicted to be a semiconductor. We further clarify the fundamental criteria governing interstitial electron localization and establish systematic correlations between superconductivity and key electronic and vibrational descriptors, including the electronic density of states, electron-phonon coupling strength, and phonon softening across all predicted phases. These results substantially broaden the structural diversity of the Li-Pt system and underscore the intriguing coexistence of superconductivity and semiconducting behavior in lithium-based electride materials.

Current-induced spin-orbit torques (SOTs) provide a crucial mechanism for the electrical control of antiferromagnetic order. However, SOTs in antiferromagnets (AFMs) and the resulting spin dynamics remain largely unexplored. Here we present a complete classifications of SOTs in bulk collinear AFMs based on magnetic point group symmetry. Depending on the symmetry operations that connect the two antiparallel spin sublattices, the SOTs are categorized into six distinct types. We focus on three representative AFMs in which the spin sublattices are linked by fractional translation, spatial inversion, or neither of these symmetries, respectively. Using first-principles calculations within Kubo linear response theory, we compute the SOTs on each sublattices, and simulate the Néel vector dynamics via the Landau-Lifshitz-Gilbert equation. In the prototypical $\mathit{PT}$-symmetric AFM and the inversion symmetry breaking altermagnet, our simulations reveal that deterministic Néel vector switching can be driven entirely by field-like torques. Moreover, all-electrical writing of a single domain state with preset Néel vector direction, as well as ${180}^{\circ }$ deterministic switching is attainable. This work sheds light on current-controlled antiferromagnetic orders in collinear AFMs. In particular, for the inversion symmetry breaking altermagnet, the demonstrated electrical writing and reading of the Néel vector hold promise for antiferromagnetic memory applications.

In this study, MnP single crystals were synthesized and comprehensively characterized to elucidate their structural quality, magnetic behavior, magnetocaloric response, and field-dependent critical phenomena along the easy $c$ axis. High-resolution x-ray diffraction confirmed the orthorhombic MnP-type crystal structure with excellent crystallinity. At the same time, magnetization measurements revealed a sharp ferromagnetic transition near room temperature. To further understand the underlying physics governing these behaviors, the critical exponents β, γ, and δ were systematically extracted in three distinct magnetic-field regimes, low, medium, and high, thus enabling a detailed assessment of universality and crossover effects in this anisotropic itinerant ferromagnet. In the low-field regime, we obtained a Curie temperature $T_{\mathrm{C}}=288.69\pm 10.01\mathrm{K}$, with critical exponents $\beta =0.355\pm 0.016, \gamma =1.208\pm 0.021$, and $\delta =4.407\pm 0.167$. For medium fields, the transition sharpened and shifted toward higher temperature, yielding $T_{\mathrm{C}}=294.52\pm 4.08\mathrm{K}, \beta =0.368\pm 0.022, \gamma =0.995\pm 0.010$, and $\delta =3.701\pm 0.031$. In the high-field regime, the system displayed a pronounced crossover from nearly second-order to more mean-field-like behavior, with $T_{\mathrm{C}}=300.26\pm 2.00\mathrm{K}, \beta =0.490\pm 0.049, \gamma =1.058\pm 0.035$, and $\delta =3.158\pm 0.227$. These systematic variations indicate strong field sensitivity of the magnetic interactions and highlight a continuous evolution of the critical behavior across the three regimes. The intrinsic thermodynamic $T_{\mathrm{C}}$ is approximately 296 K, while the field-dependent values extracted from modified Arrott plot/Kouvel-Fisher analyses represent effective crossover temperatures. This work provides a unified picture of the structural, magnetic, magnetocaloric, and critical properties of MnP single crystals. The field-dependent critical exponents demonstrate that MnP exhibits nonuniversal scaling governed by magnetic anisotropy and external-field strength, offering valuable insight into both fundamental studies of criticality and the optimization of MnP-based magnetocaloric materials near room temperature.

In this work, we investigate the bi-isotropic effects in the formation and tunability of hybrid surface polaritons in bilayer configurations. To do that, we consider a heterostructure constituted with layers formed by a TI medium endowed with bi-isotropic constitutive relations and an AFM medium. Using transfer matrix formalism, we derive general dispersion relations for surface polaritonic modes including the bi-isotropic coupling parameter, and analyze their coupling to bulk magnon-polaritons in the AFM layer. As an illustration, we consider a heterostructure formed with ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ interfaced with antiferromagnetic (AFM) materials that support terahertz-frequency magnons. In the non-null bi-isotropic coupling regime, the surface Dirac plasmon-phonon-magnon polariton (DPPMP) dispersion undergoes a pronounced redshift, accompanied by the suppression of the characteristic anticrossing between the Dirac plasmon and the phonon. This effect, observed for all AFM materials considered, suggests a weakening of the hybrid interaction, possibly due to saturation or detuning mechanisms induced by the increased $\alpha$ parameter. The latter yields a redshift that partially compensates the blueshift induced by a higher Fermi level, restoring the system to a weak-coupling regime analogous to that observed at lower Fermi energies. Our findings reveal that both the Fermi level and the bi-isotropic response offer independent and complementary control parameters for tuning the strength of light-magnon coupling in TI/AFM heterostructures, with potential implications for reconfigurable THz spintronic and photonic devices.

The variational quantum eigensolver (VQE) has been widely used to find the ground state energy of different Hamiltonians with no analytical solutions that are classically difficult to compute. In our work, we use the VQE to identify the phase transition boundary for an infinite-order phase transition. Typically, in a finite-order phase transition, finite-order derivatives of the ground state energy would signal the phase transition. However, that is not the case for infinite-order phase transitions, for which a global-range order parameter is required. In this work, we use a long-range XXZ (LRXXZ) chain for our study. It has been observed that two types of phase transitions for this model exist. One is a first-order phase transition, straightforwardly evaluated using the gradient of the ground energy. The second is an infinite-order phase transition, which is conventionally unfeasible to evaluate using the ground state energy. Therefore, it has been observed that the ground state energy is not sufficient to probe both of these transition boundaries. However, we propose a simple technique to utilize the ground state energy from the VQE to identify both phase transitions. The idea stems from the argument that the VQE requires an ansatz circuit; therefore, the accuracy of the VQE relies on this ansatz circuit. We have designed the ansatz circuit such that the estimated ground state energy is sensitive to the phase it is evaluated in. It is achieved by applying the constraint that the net spin remains constant throughout the optimization process. Consequently, the ansatz works in a certain phase in which it gives a relatively small random error, as it should, when compared to the error in the ground state energy calculations of the other phases, in which the ansatz fails. Identifying these changes in the behavior of the error in the ground state energy evaluation using the VQE, we are able to identify the phase boundaries. Using Exact Diagonalization (ED), we also compare the behavior of the energy gradient and energy gap across both phase transition boundaries for this model. Further, by increasing the depth of the optimization circuit, we also accurately evaluate the ground energy of the LRXXZ chain for $J>0$ and $J<0$ in the paramagnetic region.

All-inorganic lead halide perovskites $\mathrm{CsPb}{\mathrm{X}}_3$ (X = Cl, Br, I) exhibit rich structural dynamics, with vibrational properties and electron-lattice interactions still under active investigation due to strong lattice anharmonicity and structural phase transitions. Here we present a first-principles study of $\mathrm{CsPbB}{\mathrm{r}}_3$ across its orthorhombic, tetragonal, and cubic phases. We analyze the impact of the structural phases on the phonon dispersions, by including lattice anharmonicity. We discuss the validity of the semiclassical Fröhlich Hamiltonian, by quantifying the electron-phonon coupling strength for individual polar optical phonons, analyzing the mixing induced by long-range polar interactions and the relative contributions to the dielectric spectrum, tracing their symmetry evolution using group theory and a band folding approach. Despite pronounced structural transformations and enhanced anharmonicity at elevated temperatures, the long-range polar coupling mechanism associated with a single longitudinal optical mode lying at high frequency remains dominant throughout the entire temperature range. Furthermore, we show that, in the absence of symmetry-breaking effects, effective cubic models accurately capture long-range field behavior in low-temperature phases. This work establishes a microscopic foundation for a better understanding of polarons and exciton-polarons in bulk $\mathrm{CsPbB}{\mathrm{r}}_3$ and related nanostructures.

Critical states in quasiperiodic systems defy the conventional dichotomy between extended and localized states. In this work, we demonstrate that non-Hermiticity fundamentally reshapes this paradigm by giving rise to a class of quasiperiodic skin criticality. We introduce a non-Hermitian quasiperiodic lattice based on a modulated Hatano-Nelson model and uncover a universality class of quasiperiodic skin criticality, in which all eigenstates share an identical multifractal spatial structure. Through a nonunitary gauge transformation, the system is mapped onto a disorder-free lattice, enabling exact analytical solutions for the full spectrum and eigenstates. As a consequence, the inverse participation ratio is strictly energy independent and controlled solely by a global phase. We further show that these collective critical features persist in multiband lattices, establishing a general and analytically controlled framework for non-Hermitian quasiperiodic criticality.

We investigate the influence of correlations and plasmonic excitation on the valence band satellite of $\alpha$-Fe, along with magnetic and spectral properties as a function of temperature. Coulomb interaction parameters are obtained by systematically employing various schemes within the constrained random-phase approximation (cRPA). This study identifies the presence of valence band satellite in Fe at $\sim 6\mathrm{eV}$ binding energy supported by (i) substantial incoherent spectral weight in the valence band spectra obtained from Density Functional Theory plus Dynamical Mean Field Theory $(\mathrm{DFT}+\mathrm{DMFT})$ and (ii) plasmonic excitations in the frequency range $\sim 6–8\mathrm{eV}$ suggested by $G_0{W}_0$ calculations. We note a significant contribution from the temperature-dependent Pauli spin susceptibility, indicating a competing degree of itinerancy. $e_g$ state shows a strong temperature-driven non-Fermi-liquid behavior emerging near $T_c$. Our results reveal that a high-temperature orbital-selective loss of coherence eventually leads to an orbital-selective collapse of magnetization at $T_c$, suggesting a ferromagnetic phase characterized by strong correlation- and temperature- dependent spectral features.

Photoluminescence measurements confirmed a direct band gap of ∼1.41 eV for the cubic ${\mathrm{Na}}_2\mathrm{KSb}$ phase. At the highest excitation powers, a secondary emission peak emerged alongside the original band-edge peak, indicating the formation of a Fermi-degenerate electron-hole plasma. Polarization- and temperature-resolved Raman spectroscopy, supported by density functional theory (DFT), revealed the vibrational and structural properties of multialkali antimonide high-vacuum photocathode thin films. Polycrystalline ${\mathrm{Na}}_2\mathrm{KSb}$ cubic phase of the as-grown film was explicitly identified by its characteristic transverse optical (TO - 147 $\mathrm{c}{\mathrm{m}}^{-1}$) and longitudinal optical (LO - 179 $\mathrm{c}{\mathrm{m}}^{-1}$) phonon modes. These modes exhibited exceptional thermal stability, while the LO mode intensity showed a selective, temperature-dependent quenching attributed to a weakening of the Fröhlich interaction. DFT phonon calculations for the thermodynamically stable cubic ${\mathrm{Na}}_2\mathrm{KSb}$ phase and the hexagonal ${\mathrm{NaK}}_2\mathrm{Sb}$/${\mathrm{Na}}_3\mathrm{Sb}$ polymorphs confirmed the experimental assignment of the cubic ${\mathrm{Na}}_2\mathrm{KSb}$ phase as the intrinsic structure of the as-grown film. However, the analysis revealed that high laser power density in Raman spectroscopy can induce a local phase transformation from the cubic structure to partially hexagonal ${\mathrm{NaK}}_2\mathrm{Sb}$ phase, highlighting the metastability of the material under nonequilibrium conditions. These findings provide fundamental understanding into the lattice dynamics and phase stability essential for the performance and operational limits of high-efficiency photocathodes.

Extending hyperuniformity from classical to quantum fluctuations in electron systems yields a framework that identifies quantum phase transitions and reveals underlying gap structures through the quantum weight. We study long-wavelength fluctuations of many-body ground states through the charge-density structure factor by incorporating intrinsic quantum fluctuations into hyperuniformity. Although charge fluctuations at zero temperature are generally suppressed by particle-number conservation, their long-wavelength scaling reveals distinct universal behaviors that define quantum hyperuniformity classes. By exemplifying the Aubry-André model, we find that gapped and gapless phases, as well as localized, critical, and extended phases are sharply distinguished by the quantum hyperuniformity classes. Notably, at the critical point, multifractal wave functions generate anomalous scaling behavior. We further show that, in quantum-hyperuniform gapped phases, the quantum weight provides a quantitative measure of the gap size through a universal power-law scaling. Along with classical hyperuniformity, quantum hyperuniformity class serves a direct fingerprint of quantum criticality and a practical probe of quantum phase transitions in aperiodic electron systems.

Altermagnets exhibit momentum-dependent spin splitting without net magnetization, combining characteristics of both ferromagnets and antiferromagnets, making them highly interesting for spintronics applications. CrSb is a prime candidate with a high Néel temperature ($\sim 700\mathrm{K}$) and a large exchange-driven splitting of $\sim 0.6–1\mathrm{eV}$. Using ab initio calculations, we consider slabs of various orientations in the ultrathin limit. In (0001)-oriented slabs, the exchange-driven altermagnetic spin splitting collapses, but including spin-orbit coupling restores a residual anisotropic splitting of $\sim 70\mathrm{meV}$. The (100)-oriented slabs become fully spin degenerate due to symmetry reduction. In contrast, the (110)-oriented slabs show a strong altermagnetic spin splitting of $\sim 400\mathrm{meV}$, and thus emerges as a robust candidate for realizing large, exchange-driven altermagnetism.

The ferrimagnetic Blume-Emery-Griffiths one-dimensional model on the sawtooth chain with bilinear and biquadratic interactions between spins is studied exactly. Conditions at which the characteristic feature of spin ices, the remnant entropy at zero magnetic field appears, are studied. On the other hand, we determine at which set of parameters the model manifests quasiordering. That quasiordering reveals itself in almost nondecaying correlation functions below the quasicritical temperature, the jumplike temperature behavior of the entropy, and the quasipeculiarity in the temperature behavior of the specific heat at the quasicritical temperature. We show that the temperature behavior of magnetic moments of spins and the total magnetization drastically change its properties at the quasicritical temperature. The magnetic Grüneisen parameter manifests the most dramatic changes at the temperature of the quasiordering if the latter exists and in the ground state otherwise.