Contrary to traditional approaches, high entropy oxides (HEOs) strategically employ cationic disorder to engineer tunable functionalities. This disorder, stemming from multiple elements at the same crystallographic site, disrupts local symmetry and induces local distortions. By investigating a series of single-crystalline $[{\mathrm{La}}_{0.2}{\mathrm{Pr}}_{0.2}{\mathrm{Nd}}_{0.2}{\mathrm{Sm}}_{0.2}{\mathrm{Eu}}_{0.2}{]\mathrm{NiO}}_{3-\delta }$ thin films, grown by pulsed laser deposition, we demonstrate herein that the creation of oxygen vacancies (OVs) further offers a powerful means of tailoring electronic behavior of HEOs by concurrently introducing disorder and doping electrons into the system. Increasing OV concentration via changing the oxygen partial pressure during the ablation leads to a monotonic increase in room-temperature sheet resistance. A striking feature is the Janus-faced response of the metal-insulator transition (MIT) due to the interplay among correlation energy scales, electron doping, and disorder. Unlike the monotonous influence of OV observed for the MIT in ${\mathrm{VO}}_2$ and ${\mathrm{V}}_2{\mathrm{O}}_3$, initial OV doping lowers the MIT temperature here, whereas higher OV levels completely suppress the metallic phase. Magnetotransport measurements further reveal weak localization, and strong localization as a function of relative change in $\delta$. Moreover, the disorder on both $RE$ and oxygen sublattices is responsible for the Mott-Anderson insulator state. These findings surpass the scope of the recently featured “electron antidoping” effect.

${\mathrm{CeVGe}}_3$ is a helical antiferromagnetic heavy-fermion system with an ordering temperature $T_{\mathrm{N}}=5.5\mathrm{K}$. The pressure effect on the magnetic properties of ${\mathrm{CeVGe}}_3$ via electrical resistivity and calorimetry is studied. $T_{\mathrm{N}}$ is quickly suppressed to absolute zero at the critical pressure of $0.75–0.79\text{GPa}$, suggesting the presence of an antiferromagnetic quantum critical point. The temperature-field phase diagrams are examined under different pressures. The evolution of the phase diagram under pressure demonstrates that the physical properties of ${\mathrm{CeVGe}}_3$, which are already fascinating at ambient pressure, exhibit even greater complexity under applied pressure.

Near a quantum critical point in a metal, strong fermion-fermion interactions mediated by soft collective bosons give rise to two competing phenomena: non-Fermi liquid behavior and superconductivity that deviates from conventional BCS and Migdal-Eliashberg theories. We consider the problem of obtaining closed-form analytical lower and upper bounds on transition temperatures for such systems. We focus mainly on a class of models known as the $\gamma$-model, a variation of the Eliashberg theory of superconductivity where the effective interaction potential scales as $V\left(\mathrm{\Omega }\right)\propto 1/{\left|\mathrm{\Omega }\right|}^{\gamma }$. Building on a recent reformulation of Migdal-Eliashberg theory—expressed as a classical infinite spin chain with nonlocal interactions by Yuzbashyan and Altshuler [Phys. Rev. B 106, 014512 (2022)], Yuzbashyan, Kiessling, and Altshuler [Phys. Rev. B 106, 064502 (2022)]—and employing a linear algebra analysis of the Hessian matrix obtained from the Free Energy functional, we derive rigorous, closed-form expressions for upper and lower bounds on the superconducting transition temperature for any $\gamma >0$. The main result of the paper is to establish an analytical upper bound on the transition temperature in closed form. Our upper bound is significantly tighter than those currently available in the literature and demonstrates rapid convergence toward results from prior numerical studies. Also, by applying the singularity condition directly to the unbounded Hessian matrix, our independently performed calculations confirm the lower bounds previously established in the literature by Kiessling, Altshuler, and Yuzbashyan [J. Stat. Phys. 192, 69 (2025)].

We study a dirty two-dimensional superconductor with Rashba spin–orbit coupling and in-plane Zeeman fields described by the nonlinear sigma model that includes the Cooper and long-range Coulomb interactions. The renormalized Ginzburg–Landau theory, which includes the weak localization effects at the one-loop level, is constructed using the Keldysh functional formalism. It is shown that the transition temperature and magnetic field, as well as the tricritical point appearing in the phase diagram, are suppressed by the interactions. Nevertheless, we have found a universal behavior in the high-transition-temperature regime that demonstrates the robustness of the superconducting diode effect against interactions. The conductivity of the resistive states emerging after the superconducting states are destroyed by the critical current is also calculated, and localization behavior is demonstrated.

Unlocking superconductivity in the intrinsically nonsuperconducting noble metals Au, Ag, and Cu represents a fundamental challenge in low-dimensional quantum materials. While quantum confinement in the atomically thin limit is known to trigger emergent superconductivity, strategies to amplify this marginal effect to experimentally accessible temperatures remain a key open question. Using first-principles calculations, we establish a unified framework linking intrinsic confinement effects with interface engineering in noble metal films. We reveal that intrinsic superconductivity is element specific: It is suppressed in Ag by a stiff phonon spectrum but emerges in trilayer Cu with $T_{\text{C}}\approx 0.78\mathrm{K}$ and pentalayer Au with $T_{\text{C}}\approx 0.63\text{K}$ driven by confinement-induced density of states (DOS) enhancement and phonon softening, respectively. In hexagonal boron nitride (h-BN)/Cu(111) heterostructures, $T_{\text{C}}$ is critically dictated by the interfacial stacking configuration. The thermodynamically stable N-bonded interface provides an experimentally accessible superconducting state with $T_{\text{C}}\approx 3.23\mathrm{K}$, whereas a metastable B-bonded configuration boosts $T_{\text{C}}$ to 7.00 K. A detailed analysis reveals that the enhancement is caused not by charge transfer or a simple increase in the DOS, but by an interface-induced Lifshitz transition that reshapes the Fermi surface and amplifies momentum-resolved electron-phonon coupling matrix elements. This Lifshitz-controlled mechanism persists in bilayer h-BN/trilayer (3L) Cu(111) and is further reproduced in heterometallic 3L-Au/Ag(111), highlighting its transferability beyond a specific interface configuration. Our work unifies the understanding of intrinsic two-dimensional superconductivity with atomistic interface design and identifies interface-controlled Fermi surface topology as a route to functionalizing noble metals as emergent superconductors.

High-pressure superconducting electrides have attracted extensive attention because of the coexistence of accumulated interstitial electride states (IAEs) and the superconducting state, providing a novel platform for exploring high-temperature superconductors. Nevertheless, the driving force behind the formation of the superconducting state without pressure effect in electrides remains unclear, particularly how intrinsic IAEs reconciling within the high-locality nature, as per the traditional view, effectively form Cooper pairs. Here, we have revealed the correlated superconducting state intertwined with IAEs in the electride $Pm\text{−}3m\text{-H}{\mathrm{f}}_4\mathrm{C}$ at ambient pressure, which is identified through high-throughput screening combined with element substitution. Our first-principles calculations uncover IAEs distributed within the energy range from the maximum of the effective potential to the Fermi level, indicating delocalized behaviors dominate the electronic density. Of particular note, these IAEs, characterized by forming hybridized electronic states with Hf-$d$ orbital components above unbound-state bands, are scattered by low-frequency phonon modes associated with hafnium atoms, resulting in electron-phonon coupling interaction with a critical temperature of 3.95 K. Our results elucidate the physical picture of the distribution of IAEs in energy space and their positive correlation with pressure-independent superconducting states, offering a unique perspective for understanding superconducting electrides.

Helium, which is on par with neon, is one of the most inert elements and most difficult elements for metallization in the periodic table. It requires more than 30 TPa to transit to an indirect metal. Here, via an ab initio evolutionary algorithm, we predict a semimetal helium–oxygen compound, ${\mathrm{He}}_3\mathrm{O}$, which stabilizes at 5.74 TPa with topological nodal lines in its band structure. Further analysis revealed definite chemical bonding between the He and O atoms. Since helium and oxygen exist widely in the white dwarfs, ${\mathrm{He}}_3\mathrm{O}$ is quite important for understanding and modeling celestial bodies.

The graphite-to-diamond phase transition under high pressure and high temperature remains incompletely understood at the atomic scale, particularly the path-dependent mechanisms of interface formation and growth. Using large-scale deep potential molecular dynamics simulations, we systematically investigate the phase transition dynamics along three distinct compression pathways: hydrostatic, interlayer uniaxial, and intralayer uniaxial compression. While all pathways yield cubic diamond as the primary product through a nucleation and growth mechanism, the transformation pathways exhibit remarkable path dependence. We reveal that hydrostatic and interlayer uniaxial compressions favor anisotropic diamond growth via coherent interfaces, whereas intralayer compression induces quasi-isotropic growth mediated by defects. The coherent interface promotes preferential growth along the ${\left[210\right]}_{\text{HG}}$ direction due to elevated atomic stress, strain energy minimization, and lower interface formation energy. In contrast, intralayer uniaxial compression induces nucleation through a wavelike buckling and slipping process, resulting in quasi-isotropic growth mediated by defect-suppressed interface propagation. Our findings reveal how compression pathways control both nucleation mechanisms and growth dynamics, advancing the understanding of coherent-interface-governed transformations in carbon materials.

We investigate the physical properties of elementary magnon excitations of the ordered antiferromagnetic Heisenberg model on the honeycomb lattice using quantum Monte Carlo (QMC) simulations, series expansions (SE), and continuous similarity transformations (CST). The stochastic analytic continuation method is used to determine the dynamic structure factor from correlation functions in imaginary time obtained by QMC. In contrast to the “roton minimum” of the square lattice Heisenberg antiferromagnet, we find that magnons on the honeycomb lattice completely decay in the corner of the Brillouin zone ($K$ point); the entire weight is shifted into the continuum. These findings are fully supported by SE and CST in momentum space. The extrapolated one-magnon dispersion obtained from SE about the Ising limit quantitatively agrees with the extracted QMC excitation energies except around the $K$ point, where large uncertainties in the extrapolation indicate the magnon decay. This quantum decay is further confirmed and understood by the CST, which yields a divergent flow when enforcing a magnon quasiparticle picture. The divergence originates from strong attractive magnon-magnon interactions leading to a bound state and thereby to a three-magnon continuum overlapping with the one-magnon state. This has the magnon quasiparticle picture break down at high energies on the honeycomb lattice.

We study the Hofstadter model on a hexagonal lattice with irrational magnetic flux in this work. The Hofstadter model of the square lattice with irrational flux has been solved mathematically by Avila [Invent. Math. 210, 283 (2017);Acta Math. 215, 1 (2015)] and his collaborators in his Fields medal work. However, this theory is usually not applicable to lattices with internal degrees of freedom, such as spin or sublattices. In this work, we show that for the hexagonal lattice with only nearest-neighbor hoppings, the system can still be characterized by a $2\times 2$ transfer matrix and solved exactly by Avila's global theory, although this lattice has two sublattices. We obtained the exact localization phase diagram of the hexagonal lattice with irrational flux by this theory, which reveals three pure phases, i.e., the extended, localized, and critical states but no mobility edge due to the chiral symmetry. We used the renormalization group (RG) theory to verify these results, which can determine part of the phase diagram. We then computed the fractal dimension of the remaining part numerically. The results from both the RG theory and numerical analysis confirmed the phase diagram we get from Avila's global theory. Our results may be tested in various hexagonal moiré lattices and artificial superlattices achieved in recent experiments.

The optical response of two-dimensional materials is often significantly impacted by excitonic effects due to the reduced screening of attractive Coulomb interactions in low-dimensional systems. Accurate modeling of exciton formation and real-time dynamics is essential to understanding their ultrafast optical properties. In this study, we theoretically investigate the exciton dynamics in a two-dimensional hexagonal boron nitride (h-BN) and a germanium sulfide (GeS) monolayers exposed to an ultrashort laser pulse. We analyze the system's response to the external field in one- and two-photon excitation regimes. For our calculations, we combine a state-of-the-art ab initio approach to study exciton dynamics with a highly precise numerical scheme. We incorporate electron-hole interactions through a nonlocal self-energy operator derived from the many-body perturbation theory (MBPT) within the time-dependent adiabatic $GW\left(\mathrm{TD}\text{−}\mathrm{a}GW\right)$ approximation. We implement this approach using the full-electron $\mathrm{LAPW}+\mathrm{lo}$ method in the all-electron exciting package. Our results elucidate the role of many-body effects in shaping ultrafast excitonic processes in two-dimensional materials, contributing to the fundamental understanding necessary for optoelectronic and photonic applications.

Emerging polar nitride perovskites have recently attracted considerable attention for ferroelectric photovoltaic applications owing to their smaller band gaps compared with conventional oxide perovskites. Carrier mobility is a key performance parameter governing charge transport and device efficiency; however, quantitative understanding of carrier mobility in nitride perovskites remains limited. Here, we systematically investigate the charge-carrier transport properties of eight nitride perovskites using first-principles density-functional theory combined with Boltzmann transport calculations. The results reveal that these materials exhibit bandlike transport behavior, with room-temperature carrier mobilities ranging from 2 to $23\mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$. These values are comparable to those of doped ${\mathrm{SrTiO}}_3$, but somewhat lower than those of typical halide perovskites. Among the investigated compounds, $\mathrm{YW}{\mathrm{N}}_3$ exhibits the highest electron mobility ($22.19\mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$), whereas $\mathrm{CeTa}{\mathrm{N}}_3$ shows the highest hole mobility ($22.16\mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$). We identify piezoelectric scattering as the dominant mechanism limiting carrier mobility in most of the investigated nitride perovskites, while polar optical phonon scattering plays a comparable role. In contrast, polar optical phonon scattering becomes the primary mobility-limiting mechanism in $\mathrm{CeNb}{\mathrm{N}}_3$ and $\mathrm{YMo}{\mathrm{N}}_3$, reflecting stronger electron-phonon coupling in these compounds. Furthermore, we develop two simplified conceptual models to explain the observed mobility trends across the material series. Based on these models, Young's modulus and carrier effective mass are identified as the key physical descriptors governing carrier mobility in nitride perovskites. Our results establish the intrinsic mobility limits and provide fundamental insights into carrier transport in nitride perovskites, offering important guidance for the design and optimization of nitride-perovskite-based ferroelectric photovoltaic devices.

The study of electron hydrodynamics provides a powerful framework for understanding transport in ultraclean conductors, yet experimental evidence has thus far been largely restricted to the linear response regime. Here, we report the direct observation of a strongly nonlinear transport regime in a high-mobility two-dimensional electron system. By engineering devices in a Venturi-shaped (wedge) geometry specifically designed to enhance convective nonlinearities, we uncover a pronounced nonlinear voltage response and a large diodicity in the current-voltage characteristics. Our experimental findings show quantitative agreement with a theoretical model that attributes the observed nonlinearity to the convective acceleration of the electron fluid, analogous to the Bernoulli effect. These results provide compelling evidence for the applicability of the hydrodynamic framework to electron transport in two dimensions and open avenues for exploring nonlinear and preturbulent phenomena in solid-state systems.

Flat bands are typically associated with finely tuned moiré systems in two dimensions. Here we show that twist stacking faults in bulk rhombohedral graphite generically produce nearly flat interface bands governed by the interplay between the moiré periodicity and Zak phase topology. We identify a condition for the emergence of flat bands across the entire moiré Brillouin zone associated with the extent of nontrivial Zak phase in momentum space. Using complementary continuum and tight-binding approaches, we demonstrate the evolution of these interface states and their dominance near the Fermi level. We further show that the flat bands host tunable topological character, with disorder driving a controlled evolution, and predict that the disorder will eventually make the valley Chern number vanish.

The misfit layered compound ${\left(\text{PbS}\right)}_{1.11}{\mathrm{VS}}_2$ shows a complex interplay of structural modulation, disorder, and charge dynamics that leads to unconventional magnetic and transport properties. High resolution scanning transmission microscopy and temperature-dependent single crystal x-ray diffraction reveal short-range layer clustering, fractional layer sliding, diffuse scattering, and an appearance of new reflections below $T_{\text{s}}=220\mathrm{K}$, consistent with a continuous structural transition involving $c$-axis doubling and strengthened interlayer coupling. Below $T_{\text{s}}$, the resistivity increases by orders of magnitude and evolves into variable-range hopping; the data are most consistent with Efros-Shklovskii behavior driven by disorder-induced localization. The magnetoresistance is large, weakly anisotropic, and quadratic at low temperature, but at intermediate temperatures shows a complex shape, reflecting competing scattering and localization processes. Overall, the electronic state of ${\left(\text{PbS}\right)}_{1.11}{\mathrm{VS}}_2$ emerges from the combined action of structural modulation, disorder, and correlations with no single dominant mechanism governing its temperature-dependent electronic and magnetic behavior.

Using density functional calculations and multiorbital, multiatom cluster exact diagonalization that includes local exchange and Coulomb interactions, we explored the local low-energy electronic states of trilayer ${\mathrm{La}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$ via a minimal ${\mathrm{Ni}}_3{\mathrm{O}}_{14}$ cluster. We find that, at ambient pressure, starting with all three Ni being nominally $2+$ valence, one of the two extra holes is localized in the central ${\mathrm{NiO}}_2$ layer forming a Zhang-Rice singlet (ZRS) with $d_{x^2-y^2}$ orbital. The other hole mainly occupies the antibonding combination of the two interplane apical O $p_z$ orbitals and thereby hybridizes with an out-of-plane three-spin-polaron (3SP) formed by the $d_{z^2}$ orbitals of three ${\mathrm{NiO}}_2$ layers. At high pressure, however, the two extra holes are concentrated on one of two outer layers and the inner layer separately forming the ZRS with $d_{x^2-y^2}$ orbitals. We highlight the similarities between the bilayer ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ and trilayer ${\mathrm{La}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$ via speculated possible charge and spin configurations as well as the in-plane 3SP on two neighboring clusters suggested by our isolated cluster results. We thereby propose that the hole transfer from apical to in-plane oxygen orbitals of outer layer generates in-plane 3SP-like quasiparticles that act as mobile carriers coupled by interlayer superexchange; while the interplane 3SP-like states may provide the pairing glue. Since the low-pressure phase lacks freely propagating in-plane quasiparticles, this scenario naturally favors SC in the high-pressure phase.

Recently developed extended Kohn-Sham theory and extended quasiparticle (QP) theory are both fundamental and important, in particular, in treating the initially excited eigenstates from first-principles. However, still the QP theory including $GW\left(\mathrm{\Gamma }\right)$ methods has been applied only to the initial ground state by almost all authors. In this paper, we want to emphasize that these theories allow one to apply $GW\left(\mathrm{\Gamma }\right)$ methods directly to an initially excited eigenstate. Using only basic and elementary arguments without using the Green's function, we explicitly demonstrate that the QP wave functions can be normalized to unity and the self-energy can be hermitized for the initially excited eigenstate. Our paper supports the conventional procedure commonly used in first-principles calculations. These theories hold when relaxation from excited states can be ignored. We propose the normalized $GW$ (NGW) approach and perform self-consistent calculations for initially excited (cationic and photoabsorbed) states of several light atoms. The resulting QP energies show good agreement with the available experimental data for excited states, as well as with the expected relationships among different QP energies, supporting the validity of the method.

In this study, one-dimensional nanoribbons of single-layer manganese phosphorus trisulfide (${\mathrm{MnPS}}_3$) are investigated using density functional theory based calculations, complemented by experimental Raman spectroscopy measurements. Cutting the ${\mathrm{MnPS}}_3$ single layers along the high-symmetry crystallographic directions yields the formation of four possible nanoribbon types: Mn-Mn-, P-P-, and Mn-P-edged armchair and a zigzag-edged one. Structural analyses reveal clear edge- and width-dependent reconstructions in armchair nanoribbons: S-S dimerization emerges selectively at Mn-terminated edges (odd-width Mn-Mn and Mn-P nanoribbons with even Mn rows), while tilted P-P dumbbells consistently form at all P-terminated edges across the entire width range. The edge reconstructions are directly observable in scanning tunneling microscopy images. Magnetically, armchair nanoribbons stabilize either Néel or dimerized Néel antiferromagnetic order, depending on the formation of S-S dimers at Mn-terminated edges, whereas zigzag nanoribbons generally favor a ferromagnetic configuration, with the exception of the two narrowest cases. Electronic band dispersion calculations show that all armchair nanoribbons exhibit semiconducting behavior, whereas all zigzag nanoribbons are metallic, except for the two narrowest ones. In armchair nanoribbons, S-S dimerization at Mn-terminated edges reduces the band gap relative to nondimerized ribbons, whereas in nondimerized ribbons the band gap increases with width. Frequency-dependent Raman activity calculations reveal the presence of characteristic vibrational modes—originating from S-S dimers, S-P bonds, and nondimerized S atoms—that serve as fingerprint signatures of the edge type of ${\mathrm{MnPS}}_3$ nanoribbons. Overall, these results demonstrate that the electronic, magnetic, and vibrational properties of ${\mathrm{MnPS}}_3$ nanoribbons are strongly governed by edge geometry and ribbon width, highlighting their potential for edge-engineered low-dimensional spintronic and nanoelectronic applications.