Fourier’s law fails when the mean free path of the energy carriers becomes comparable to the length scales and timescales over which the temperature field varies. We derive a thermodynamically consistent generalization in which the conductivity becomes a nonlocal memory operator ${\mathit{\kappa }}_{\mathrm{eff}}(\mathbf{k},\omega )$, by combining mesoscopic nonequilibrium thermodynamics with the Mori-Kubo–Zwanzig projection-operator formalism. The Onsager kernel is a tensor sum over vibrational normal modes weighted by their Bose heat capacities and relaxation functions; it satisfies the second law for any closure consistent with the fluctuation-dissipation theorem and reduces, in the relaxation-time closure, to the nonlocal conductivity of the phonon Boltzmann equation. Two consequences follow. First, direction-dependent sampling of this tensor in a pump-probe experiment makes a nominally isotropic crystal exhibit apparent conductivities ${\mathrm{\Lambda }}_z\ne {\mathrm{\Lambda }}_r$. Second, the modulation frequency does not introduce temporal memory but sets the probed wave vector through the thermal penetration depth, so that the frequency-dependent suppression of the apparent conductivity measured by time-domain thermoreflectance on Ge and SiGe alloys is a spatial-nonlocality effect, with effective lengths of $0.25–0.4\mu \mathrm{m}$. With published mean-free-path spectra and no parameter adjusted to the thermoreflectance data, the kernel reproduces the spot-size dependence of Si, the frequency dependence of the apparent conductivity of Ge and ${\mathrm{Si}}_{0.2}{\mathrm{Ge}}_{0.8}$, and the rise of the apparent interface conductance of $\mathrm{Al}/{\mathrm{Si}}_{0.99}{\mathrm{Ge}}_{0.01}$, and contains the two-channel ballistic/diffusive model as a two-sector projection.

We study the behavior of edge states in Rice-Mele model with Hubbard interaction, $U$, at half filling using density matrix renormalization group, exact diagonalization, and effective charge dynamics in Kumar representation. By increasing $U$ for a fixed dimerization, $\delta$, and staggered potential, $V$, we find the quasiparticle edge states in the charge gap to come down in energy from $V$ in the absence of Hubbard interaction to zero energy at a critical interaction, $U_c\approx 2V$. This presents an uncommon situation where the competition between $U$ and $V$ leads to zero-energy edge states, although individually neither $U$ nor $V$ favors the edge states at zero energy. Upon increasing $U$ further, the edge state energy starts increasing again until they are lost in the bulk. However, upon increasing $U$ even further, these edge states reappear in the high-energy gap. So, with Hubbard interaction, the edge states in Rice-Mele chain transmigrate from the low- to high-energy charge gap.

Parity-violating weak interactions produce extremely small energy differences between left- and right-handed chiral systems. We show that these microscopic effects may be amplified during collective phenomena such as phase transitions. The enhancement factor is proportional to the critical number of atoms, $N_c$, in the nucleus of the new phase. Measurement of the ratio of produced left- and right-handed chiral structures may provide a way to determine $N_c$. Experiments in which spin-chiral structures are formed in ${\mathrm{ZnCr}}_2{\mathrm{Se}}_4$ during a phase transition in crossed electric and magnetic fields indicate an effective amplification corresponding to $N_c\sim {10}^9–{10}^{10}$. We emphasize, however, that such large values cannot be inferred from homogeneous capillary nucleation alone, since the same parameters imply a very large nucleation barrier; in real crystals heterogeneous nucleation, defects, strain, and domain-growth dynamics may be essential. We also discuss, more cautiously, whether analogous collective enhancement could operate in first-order cosmological phase transitions beyond the standard model. The standard-model electroweak transition for the observed Higgs mass is a crossover and therefore has no critical bubble nucleus.

The Dicke-Hubbard model, describing an ensemble of interacting atoms in a cavity, provides a rich platform for exploring collective quantum phenomena. However, its potential for quantum thermodynamic applications remains largely uncharted. In this paper, a close connection between superradiance phase transition and the quantum thermodynamic applications of the Dicke-Hubbard model is established. Based on studies of the steady-state superradiant phase transition in the Dicke-Hubbard model and the thermodynamic mode of an Otto cycle with the Dicke-Hubbard model as the working substance, it is demonstrated that the steady-state synergistic mechanism under high- and low-temperature environments is the reason for the emergence of high-performance heat engines, while the competitive mechanism leads to the appearance of high-performance quantum refrigerators. A comparison of the thermodynamic behaviors of the Otto cycle with the Dicke model and the Dicke-Hubbard model as working substances reveals that the multicavity-coupled Dicke-Hubbard model achieves a higher coefficient of performance. These results not only deepen our understanding of the energy conversion mechanism in nonequilibrium quantum thermodynamics but also lay a theoretical foundation for the future experimental design of high-performance quantum Otto heat engines and refrigerators.

In this work, we report a sol-gel-based combustion process for the formulation of gallium oxide ($\beta \text{−}\mathrm{G}{\mathrm{a}}_2{\mathrm{O}}_3$) to develop robust UV-C (200–280 nm) photodetectors. Controlled Zn incorporation is employed to modulate the optical and electronic properties of $\beta \text{−}\mathrm{G}{\mathrm{a}}_2{\mathrm{O}}_3$. The devices are fabricated on a $c$-plane sapphire (0001) substrate, and a comparative analysis is performed for varying Zn dopant concentrations. Planar metal-semiconductor-metal structures with 50-µm-wide interdigitated aluminum electrode architecture are realized using standard photolithographic and processing techniques. The optimized photodetector devices exhibit a high responsivity, low rise time, and high photocurrent/dark current ratio of $\sim 20$ mA/W, $\sim 2$ s, and $\sim {10}^4$ in the UV-C range, associated with Zn-dependent modification of the material’s optical response, local electronic environment, and carrier transport/trapping processes. It establishes the Zn-doped $\beta \text{−}\mathrm{G}{\mathrm{a}}_2{\mathrm{O}}_3$ as a promising platform for robust, low-cost, and high-performance solar-blind UV-C photodetector applications.

We argue that the static dielectric constant of small (thin and/or narrow) semiconductor and insulator nanostructures depends strongly on their environment. We do so by considering the electronic response, simply reviewing, briefly but critically, the existing literature. Regarding the ionic response, in addition to reviewing the literature, we use a simple model to account for the confinement of optical phonons in thin films and show that the reduction of their density of states has a negligible effect on the dielectric constant, in contrast to some claims found in the literature. In general, we argue that in realistic structures, such as double-gated Si nanosheets, the use of the bulk dielectric constants for both the channel and the gate insulators is justified.

Quantum communication protocols based on spin chains have been extensively studied, yet their ability to transmit nonstabilizer resources has not been systematically addressed. We investigate the transport of quantum magic in spin chains through the natural dynamics of systems initialized in nonstabilizer states, and quantify the transported resource via the stabilizer norm. We analyze three experimentally feasible state-transfer protocols, ranging from noisy to (quasi)perfect transfer, including one realizable in trapped-ion platforms. We find that the geometry of the injected state strongly influences transport: States in the lower Bloch hemisphere achieve higher transfer quality, whereas states in the upper hemisphere give rise to an efficient magic transport only beyond a threshold value of the parameter controlling the tendency toward perfect transfer. These features are robust across all protocols and identify the Hamiltonian and state properties that favor high-quality transfer. Moreover, we identify a parameter region, relevant to the initial state preparation, in which the transported magic exceeds the initial encoding, indicating that such spin systems can act as magic-amplification channels. Our results establish the conditions for efficient transport of nonstabilizer resources and demonstrate quantum magic as a sensitive probe of quantum transport beyond population dynamics.

We present a framework based on the determinantal geometry of two-qubit gates. Combining the Weyl chamber representation with operator Schmidt theory, we interpret gate synthesis as a distance problem to determinantal varieties. This gives an operational geometry to the Weyl chamber, quantifying nonlocal complexity. We show that the $\sqrt{i\text{swap}}$ gate is the closest perfect entangler to the variety of local operations, and that no perfect entangler can be approximated by a local gate with average gate fidelity above $78.3\%$. The three different determinantal costs form a synthesis-adapted coordinate system that encodes nonlocal complexity and generally reconstruct the Weyl coordinates in the reduced sector.

We report that topological features of the dynamic electron density provide a microscopic electronic order parameter that directly reflects the extent of structural change during a phase transition and offers insight into its underlying mechanism. Using multipole electron-density models derived from extensive high-resolution synchrotron x-ray diffraction datasets collected on $\alpha \text{−}\mathrm{KN}{\mathrm{O}}_3$ at 100, 200, 290, and 380 K, we reconstruct the thermally convoluted dynamic electron density at each temperature. It is found that its temperature evolution quantitatively captures the progressive suppression of local symmetry breaking as the system approaches the $\alpha \to \beta$ phase transition. The topological descriptors of the electron density associated with the nitrate group exhibit a nonmonotonic temperature evolution with the initial inequivalence among the N–O bond electron densities undergoing an order-parameter-like collapse upon heating to 380 K, preceding the actual phase-transition temperature. These findings demonstrate that dynamic electron-density topology can provide valuable microscopic insight into structural phase transitions.

We investigate an extension of Harada gravity, a third-order theory proposed as an alternative to general relativity that preserves energy-momentum conservation and in which the cosmological constant arises as an integration constant. Our aim is to determine whether Harada gravity is unique under the principles that motivated its construction. We show that imposing both the existence of all Einstein solutions and energy-momentum conservation restricts the theory to only two distinct branches: general relativity and Harada gravity. We then relax each of these assumptions independently and demonstrate that, within the class of symmetric theories considered, Harada gravity remains the unique extension of general relativity.

Here, we present a detailed many-body ab initio study of the ${\mathrm{RbTlCl}}_3$ perovskite. The electronic and optical properties, both with and without spin-orbit coupling, have been calculated using density functional theory and many-body excited-state calculations. The band gap, which are indirect in nature, are found to be of 0.94 and 0.95 eV from Perdew, Burke, and Ernzerhof-based generalized gradient approximation exchange correlation functional with and without spin-orbit coupling, respectively. The optical properties have been computed using methods based on independent-particle approximation (IPA), IPA with scissor correction [independent quasiparticle approximation (IQPA)], local-field effects (LFEs) at random phase approximation level, and the Bethe-Salpeter equation (BSE). The estimated highest value of the imaginary part of the dielectric function using IQPA is $\sim 7$ at 2 eV, which slightly decreases to $\sim 5.7$ due to LFEs. Within the BSE, the peak value is obtained to be maximum at 1.6 eV with a magnitude of $\sim 10.8$, which indicates the strong excitonic effect below the scissor-corrected direct gap. A large number of bright and dark bound excitons are found, where the binding energies of four main bound bright excitons are found to be in the range of 315–365 meV. The main bound bright exciton is localized (delocalized) in the reciprocal (real) space. Also, the spectroscopic limited maximum photovoltaic efficiency is estimated to be 15.4% for a 0.5 µm thin film. Finally, the positive phonon frequencies and thermodynamical stable region obtained for this perovskite indicate its dynamical and thermodynamical stability. Using thermodynamic formalism of chemical potentials, $V_{\text{Cl}}$ ($V_{\text{Tl}}$) is identified as the most stable neutral point defect in Cl-poor (rich) environment. These findings reveal a significant excitonic effect in ${\mathrm{RbTlCl}}_3$ and provide valuable theoretical insights for discovering new potential photovoltaic materials within the inorganic perovskite family.

We formulate a weighted-Wasserstein framework for curvature statistics of cosmological large-scale structure. A coarse-grained density defines a weighted reference measure whose relative-entropy response separates into kinematic and density-induced Bakry-Émery contributions. On a Euclidean background, the latter is governed locally by $H_R=-{\nabla }^{2}ln{\rho }_R$; finite windows define density-weighted directional responses, while finite synthetic dimension subtracts a non-negative score-alignment deficit. The controlled local limit recovers the eigenvalue-threshold classification of the smoothed log-density Hessian, not a general equivalence with density-Hessian or gravitational-tidal classifiers. Independent smoothing and probe scales define a resolution flow. Controlled tests recover quadratic tensors to relative accuracy ${10}^{-9}$ or better and confirm $O\left(\varepsilon \right)$ and $O\left({\varepsilon }^2\right)$ convergence. In a periodic three-dimensional Zel’dovich mock, the specified six-direction transport tensor matches its direct finite-window reference with subpercent median error and directional correlation above 0.999 995. Rotated and enriched probe designs reveal appreciable finite-window eigenvalue and classification dependence, distinct from estimator error; a converged angular projection still has a nonquadratic directional residual. Under thinning to $f_{\mathrm{samp}}=1/16$, the six-direction internal error remains below $0.3\%$, while density reconstruction dominates the total error. At the fiducial radius, this finite-window observable has approximately $30\%$ lower normalized sampling error than the pointwise log-density Hessian, each relative to its own full-sampling reference. In the Gaussian-linear limit, curvature spectra are differential transforms of two-point statistics; finite-window and finite-dimensional observables retain additional profile and directional information beyond that limit.

Many interactions perturb (or shift) the hyperfine coupling in group-1 atoms between their nuclear spin and single valence electron. Previous work provided an approach to estimate this shift from electric-dipole interactions both during nonreactive collisions with other atoms or molecules at long range and with static electric fields. We extend this approach to estimate the shift due to a nearby conductive surface and improve all these estimates by numerically computing updated values for the characteristic energies they use. We investigate how to estimate these energies by scaling arguments and suggest how to adapt the approach to other applications. The results are relevant to pressure shifts in vapor cells, Stark shifts, and wall shifts in nanoscale devices.

The Alicki-Lindblad-Fannes (ALF) dynamical entropy measures the rate at which new information is gathered about a quantum system by inspecting its long-time evolution. After extending the ALF entropy to open quantum dynamics, we propose it as a measure of backflow of information from the environment. We show that the behavior of the open-system ALF entropy is a stronger witness than existing approaches based only on the open-system reduced dynamics. In the case of a qubit collisionally coupled to a classical spin chain, we obtain an exact expression for the open-system ALF entropy explicitly depending on the environment correlations. An extreme case shows how the information flow from environment to system corresponds to vanishing entropy production as for reversible finite quantum systems.