We present a theory of the emission spectrum of magnetoexcitons interacting with a $\nu =1$ quantum Hall state of massive Dirac fermions in monolayer transition metal dichalcogenides in high magnetic fields. Using an ab initio–parametrized massive Dirac fermion model including valley and spin degrees of freedom, combined with exact diagonalization techniques, we show that interband emission from the massive Dirac fermion magnetoexciton interacting with $\nu =1$ state directly probes intra–conduction-band excitations of the $\nu =1$ state. Many-body interactions with the filled massive Dirac fermion $\nu =1$ level yield a strong renormalization of the emission spectrum, including fully polarized emission, a pronounced redshift, and broadening relative to neutral and charged excitons. The calculated spectra are consistent with recent experiments [Klein et al., Phys. Rev. Res. 3, L022009 (2021); Klein et al., Phys. Rev. B 105, L041302 (2022); and Oreszczuk et al., 2D Mater. 10, 045019 (2023)].

Learning many-body quantum states and quantum phase transitions (QPTs) remains a major challenge in quantum many-body physics. Classical machine-learning methods offer certain advantages in addressing these difficulties. In this paper, we shift the research perspective that bypasses the need for high-fidelity quantum states by directly learning the parameters of parametrized quantum circuits. By integrating attention mechanisms with a variational autoencoder, we efficiently capture hidden correlations within the parameter distribution that encode quantum phase boundaries. These correlations enable us to extract phase transition information in an unsupervised manner and identify a data-driven generalized order parameter from the learned latent space. The framework remains robust even when the variational quantum eigensolver (VQE) converges to local minima rather than true ground states. Moreover, our framework acts as a classical representation of VQE optimization landscapes, enabling the reconstruction of complete phase diagrams. Our results demonstrate that QPT information can indeed be extracted directly from variational circuit parameters.

Single-electron spin qubits defined in quantum dots are used as building blocks of a semiconductor-based quantum computer. Readout in a scaled-up version of such a quantum computer is expected to rely on the Pauli spin blockade (PSB) mechanism. A desired functionality of PSB readout is that it reveals two bits of information on the two spin qubits that are involved in the process, such that the four computational basis states can be discriminated. In this work, we propose and quantitatively analyze an experimental procedure, based on gate reflectometry, which enables this four-state discrimination in a single measurement. We provide an intuitive recipe to maximize the contrast between the quantum capacitances of the four basis states. Focusing on silicon double quantum dots equipped with a micromagnet, we quantify how amplifier noise and phonon-mediated relaxation influence readout fidelity. Our results highlight a realistic opportunity to mitigate the overhead of readout ancilla qubits in a spin-based quantum computer.

Metals can undergo geometric quantum phase transitions where the local curvature of the Fermi surface changes sign without a change in symmetry or topology. At the inflection points on the Fermi surface, the local curvature vanishes, leading to an anomalous dynamics of quasiparticles. In this paper, we study geometric quantum critical metals that support inflection points in two dimensions and show that the decay rate of quasiparticles goes as $E^{\alpha }$ with $1<\alpha <2$ as a function of quasiparticle energy $E$ at the inflection points.

Recent angle-dependent magnetoresistance measurements in underdoped cuprates have revealed compelling evidence for small hole pockets in the pseudogap regime, including observation of the Yamaji effect in ${\mathrm{HgBa}}_2{\mathrm{CuO}}_{4+\delta }$ [M. K. Chan et al., Nat. Phys. 21, 1753 (2025)]. A key distinction between theories is their predicted Fermi volumes, measured as fractions of the square-lattice Brillouin zone: $p/4$ per pocket for spin density wave (SDW) versus $p/8$ for fractionalized Fermi liquid (${\mathrm{FL}}^{*}$), where $p$ is the hole doping. We calculate the $c$-axis magnetoresistance ${\rho }_{zz}(\theta ,\varphi )$ within the semiclassical Boltzmann formalism for both states, and using the ancilla layer model for ${\mathrm{FL}}^{*}$ in a single-band Hamiltonian. The results from the ${\text{FL}}^{*}$ phase show good consistency with current experimental data. Conversely, the results for the SDW phase are highly sensitive to the ordering momentum along the $z$ direction. An ordering vector of $Q=(\pi ,\pi ,\pi )$ yields predictions that starkly disagree with the experiment. The only possibility for agreement within the SDW scenario is to assume an ordering momentum of $Q=(\pi ,\pi ,0)$. However, even in this specific case, the SDW scenario predicts a marginally smaller Yamaji angle at $\varphi =0$ than the ${\mathrm{FL}}^{*}$ theory, and a second Yamaji peak near in-plane angle $\varphi ={45}^{\circ }$, which was not observed in the experiment. In reality, the Néel ordering vector is likely uncorrelated between adjacent layers, so that there is no coherent interlayer transport of hole-pocket quasiparticles in the SDW scenario, and consequently no Yamaji effect. Our results support the ${\mathrm{FL}}^{*}$ interpretation of Fermi arcs in the pseudogap phase and establish Yamaji angle measurements as a discriminatory tool between theoretical models.

In this study, we investigate the interpretation of the Stokes shift (SS) by employing the optoelectronic reciprocity relation (ORR), which provides a fundamental link between optical absorption and emission processes. We first revisit the van Roosbroeck-Shockley relation and the generalized Planck's law, both of which have been widely used in conventional analyses of the SS. While these relations are valid when the quasi-Fermi level splitting (QFLS) is spatially uniform within the optically active region, it becomes difficult to accurately reproduce photoluminescence spectra from absorption measurements in the presence of parasitic optical absorption that is not accompanied by QFLS. Such parasitic absorption can originate from free-carrier absorption, absorption in nonactive layers such as transparent electrodes and antireflection coatings, as well as absorption via defect-related states. To overcome this limitation, we apply ORR to a quantum-structured superlattice solar cell exhibiting a sharp excitonic absorption peak. External quantum efficiency (EQE) spectra are measured and subsequently used to calculate electroluminescence (EL) spectra via ORR. A direct comparison between the calculated and measured EL spectra, together with the measured EQE, demonstrates that the experimentally observed SS is quantitatively reproduced within the ORR framework, with the reconstructed EL peak coinciding at 943 nm (within the 1 nm spectral resolution) and with close agreement in spectral line shape. This result demonstrates at the device level that the observed SS is consistent with the detailed-balance relation between optical absorption and carrier recombination. The analysis further shows that ORR provides a practical framework for evaluating the SS in the active region while reducing the influence of parasitic absorption processes that do not contribute to collected carriers.

Nanoporous carbons and carbon nanostructures can store hydrogen at cryogenic temperatures but lack the volumetric and gravimetric capacity to be industrially significant. Recent inelastic neutron scattering experiments suggest a highly dense phase of hydrogen at temperatures well above the melting point of solid hydrogen. However, it remains unclear how pore geometry and intermolecular interactions enable these dense phases to exist, with dispersion (van der Waals) or electrostatic/induction suggested to be the key effects in slit and curved pores but their relative contributions have yet to be quantified. In this paper, we perform benchmark electronic structure calculations allowing the interactions between planar and curved aromatic molecules with hydrogen to be accurately determined. Dispersion was found to dominate over electrostatic and inductive effects with some many-body charge transfer (Dobson type-A) effects needed to capture the most highly curved structures. Density functional methods that include type-A many-body effects were found to accurately describe the intermolecular interactions at a fraction of the cost of coupled-cluster simulations and these approaches were used to calculate the energies inside large carbon bowl and slit pores. The interaction energies inside the bowl pores were found to depend on the orientation of the hydrogen molecule. This rotational barrier, modeled as a quantum hindered rotor, could reproduce the peak splitting observed in inelastic neutron scattering experiments, with weak splitting arising from bowl-like fullerene pores and strong splitting from highly confining nanotubelike pores. Increasing the fraction of such curved pores in nanoporous carbons may therefore offer a pathway to enhance their hydrogen-storage capacity. Moreover, the preferential adsorption of ortho hydrogen on nanotubelike pores could enable the storage of high-density hydrogen without the need to remove heat produced during the ortho-para hydrogen conversion.

Charging energy ($E_C$) is essential in quantum dot (QD) devices. Previous studies on PbTe QDs have reported both the presence and absence of $E_C$. To resolve this ambiguity, we vary the QD size, i.e., the cross-sectional area of PbTe nanowires, and track the evolution of $E_C$. For large cross-sectional areas ($\sim 16000{\mathrm{nm}}^2$), the PbTe QDs exhibit no measurable $E_C$, while quantized levels are well resolved. Decreasing this area successively to 5000, 1500, and $460{\mathrm{nm}}^2, E_C$ becomes finite and increases to 80, 160, and $210\mu \mathrm{eV}$, respectively. We further demonstrate the strong tunability of local gates, which can tune the PbTe device from the QD regime to the regime of ballistic transport. These results address concerns regarding the large dielectric constant of PbTe and provide key insights in engineering advanced PbTe quantum devices.

When single-shot readout protocols are adapted for multilevel systems, theoretical $T_1$ lifetime calculations often fall short of capturing the experimental lifetime trends. We identify extrinsic population dynamics as the fundamental origin of this disparity, establishing that the lifetime estimates can, in certain operating regions, be distinct from the intrinsic $T_1$ time. We clarify these aspects with an integrated theory to address recent measurements [Nat. Nano 20, 494 (2025)] on spin-valley states in bilayer graphene. While confirming that phonon and Johnson noise are the dominant intrinsic sources, we show that the inclusion of extrinsic factors provides the critical match to the experimental estimates. The extrinsic factors also effectuate violations of generalized Matthiessen's rules. With an improved handle on the design space, a revised readout protocol to estimate the $T_1$ lifetime of the valley qubit is proposed.

The geometry and electronic properties of nanostructures such as chains, wires, and ribbons, which are restricted in two dimensions, give rise to novel and unexpected physical phenomena. We derive the screened Coulomb potential in one-dimensional (1D) systems by solving the Poisson equation for different spatial distributions of the responding electron gas across the cross section, characterized by a 1D static electronic polarizability ${\alpha }_{1\mathrm{D}}$. Both local and nonlocal screening responses are examined. Starting from three different bare soft-core or truncated potentials of the 1D hydrogen atom, we construct seven corresponding models for the screened interaction. These screened model potentials are then applied to describe exciton binding energies using a variational approach with a trial function based on the ground-state wave function of the 1D hydrogen atom. We explicitly study atomic wires composed of ${\mathrm{MgN}}_2, {\mathrm{S}}_3, {\mathrm{Te}}_3, {\mathrm{As}}_2{\mathrm{S}}_3$, and ${\mathrm{Bi}}_2{\mathrm{Te}}_3$. The required parameters, including wire geometry, static electronic polarizability, and effective electron and hole masses, are computed within density functional theory. We find that reduced screening at short distances and antiscreening at longer distances lead to extraordinarily large exciton binding energies in the range of 1-4 eV. For extremely thin atomic wires, binding energies even larger than the values without screening are predicted. The exciton binding energy $E_B$ and radius $r_B$ obtained from the variational treatment are compared with ab initio results from many-body perturbation theory using the $GW$ approximation and solutions of the Bethe–Salpeter equation. Chemical trends are traced back to material parameters such as electronic polarizability and effective interband masses. From the comparison with the first-principles results, we identify the most accurate screening model for 1D systems.

We predict a field-free transverse Josephson diode effect in altermagnets (AMs) with Rashba spin-orbit coupling, achieving diode efficiencies exceeding $3000\%$ and unidirectional transverse supercurrents in four-terminal junctions. In this geometry, a longitudinal phase bias generates transverse supercurrents that exhibit nonreciprocity and a finite anomalous phase shift, while the longitudinal current itself displays a Josephson diode effect. Both responses are tunable via the Néel vector orientation. We further show that the effect remains robust against moderate disorder, imperfect interfaces and persists up to the superconducting transition temperature. These results establish AMs as a promising platform for nonreciprocal superconducting transport, with clear routes toward experimental realization.

The recent discovery of high-temperature superconductivity in pressurized nickelates has renewed interest in the broken-symmetry states of their ambient-pressure parent phases, where a density wave (DW) order emerges and competes with superconductivity, but its microscopic origin remains unresolved. Using ultrafast optical spectroscopy, we track quasiparticle relaxation dynamics across the DW transition at $T_{\mathrm{DW}}\approx 136\text{K}$ in trilayer nickelate ${\mathrm{La}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$ single crystals, revealing the opening of an energy gap of $\sim 52$ meV. Multiple coherent phonons, including $A_g$ modes near 3.88, 5.28, and 2.09 THz, display pronounced mode-selective anomalies across the transition, indicating that the DW is strongly coupled to lattice degrees of freedom and suggesting an important role of electron-phonon coupling. At higher excitation densities, the DW is nonthermally suppressed, producing a temperature-fluence phase diagram that parallels pressure-tuned behavior. These results establish the DW in ${\mathrm{La}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$ as a lattice-entangled instability involving multiple phonon modes, and highlight ultrafast optical excitation as a nonequilibrium tuning parameter for suppressing density wave order in nickelates.

Spatial heterogeneity is an intrinsic structural characteristic of amorphous materials and has been shown to be closely linked to numerous physical properties. However, its correlation with crystallization behaviors, particularly in phase-change materials, remains poorly understood. Here, we systematically investigate the spatial heterogeneity and medium-range order (MRO) in amorphous $\mathrm{G}{\mathrm{e}}_2\mathrm{S}{\mathrm{b}}_2\mathrm{T}{\mathrm{e}}_5$ (GST) materials using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and atomic electron tomography (AET), complemented by differential scanning calorimetry (DSC) to analyze the crystallization kinetics. We reveal that the correlation length of spatial heterogeneity increases progressively with subglass transition-temperature (sub-$T_{\mathrm{g}}$) annealing time, accompanied by the growth and interconnection of crystal-like MRO networks. Concurrently, the crystallization activation energy decreases markedly. Our findings reveal a relationship between MRO-associated enhancement of spatial heterogeneity and the reduced kinetic barrier to primary crystallization, offering a promising route to optimize phase-change memory performance via precisely controlled thermal annealing protocols.

Superfluidity in ${}^3\mathrm{He}$ exhibits many unique properties that are of interest to modern condensed matter research, including multiple superfluid phase transitions, topological defects, and exotic classes of excitations like Majorana and Weyl fermions. Many of the most interesting theoretical proposals, which remain underexplored, are realized in highly confined geometries, where surface effects play a dominant role in the thermodynamic and hydrodynamic properties. We have developed nanofluidic resonators capable of exciting a fourth-sound acoustic mode in thin channels with a highly confined dimension ($750\text{–}1800$ nm) that is only $1\text{–}2$ orders of magnitude larger than the superfluid coherence length. When a sufficiently large drive force is applied, we observe a nonlinear softening of the resonance that we interpret as due to the flow suppression of the superfluid gap. We have developed a model of the device that allows the resonance amplitude to be calibrated into a superfluid velocity, which exhibits critical behavior at particular velocities. We identify one of the observed critical velocities as being the velocity at which the gap component parallel to the flow is suppressed to zero. We compare the calibrated velocity to the prediction of a Ginzburg-Landau model, and find reasonable agreement. This measurement represents an ongoing effort to link the hydrodynamic measurements of these nanofluidic devices to theoretical predictions regarding surface gap suppression and surface-bound states.

Bistability, or the coexistence of two stable phases, can be broken by a bias field $h$ destabilizing one of the phases via the nucleation and growth of defects. Strong long-range interactions, $1/r^{\alpha }$ with $\alpha$ less than the system's dimensionality $d$, can suppress the proliferation of defects and restore bistability. The case of weak long-range interactions $d<\alpha <d+1$ remains instead poorly understood. Here, we show that it supports apparent bistability: While the system has in principle a unique stable phase, it appears bistable for all practical purposes for $\alpha <{\alpha }_c$, with ${\alpha }_c>d$ behaving as a genuine critical point. At the core of this is an exponential scaling of the critical droplet size $R_c\sim h^{-1/(\alpha -d)}$ with $\alpha$, which makes nucleating destabilizing droplets extremely unlikely for $\alpha <{\alpha }_c$, and such that ${\alpha }_c$ is mostly independent of system size. In support of these conclusions we provide field-theoretical arguments and numerics on a probabilistic cellular automaton. Overall, our results offer a way to rethink phase stability in systems with long-range interactions as well as another route to achieve practical bistability.

Thermal transport in amorphous materials involves a complex interplay between anharmonicity and atomic-scale dynamics, particularly across the glass transition. To elucidate the underlying mechanisms, we investigate the temperature dependence of thermal transport in amorphous ${\mathrm{Al}}_2{\mathrm{O}}_3$ by combining homogeneous nonequilibrium and equilibrium molecular dynamics (HNEMD and EMD) with the Wigner transport equation (WTE), complemented by structural and dynamical analyses. The thermal conductivity exhibits a significant nonmonotonic temperature dependence, increasing at low temperatures, showing a weak suppression in the glassy regime, and rising again above the glass transition temperature $T_g$. Below $T_g$, heat transport is primarily governed by vibrational excitations and is strongly modulated by anharmonic effects. The WTE framework further reveals that this behavior originates from a competition between two vibrational transport channels: population transport suppressed by anharmonic scattering, and coherence contributions enhanced by intermode coupling. Above $T_g$, strong atomic diffusion renders a purely vibrational description incomplete. EMD decomposition shows that atomic diffusion substantially enhances the kinetic contribution to heat transport. Meanwhile, strong anharmonic interactions give rise to a pronounced negative kinetic-potential cross correlation. This compensating effect, in turn, partially suppresses the rapid increase of the total thermal conductivity with temperature. Element- and coordination-resolved analyses further demonstrate that low-coordination oxygen species exhibit enhanced per-species dynamical activity, which plays a key role in strengthening the kinetic contribution to heat transport at high temperatures.

Although BCS wave functions for superconductors under periodic boundary conditions are well established, obtaining an explicit form of the many-body BCS wave function under open boundary condition is usually a nontrivial problem. In this work, we construct the exact BCS ground-state wave function of a one-dimensional spin-$\frac{1}{2}$ superconductor with $p+is$ pairing symmetry under open boundary conditions for special sets of parameters. The spin magnetization on the edges is calculated explicitly using the obtained wave function. Our work is useful for obtaining deeper understandings of open $p+is$ superconducting chains on a wave-function level.

Moiré superlattices (MSLs) in van der Waals heterostructures have demonstrated their incredible power in driving emergent electronic phenomena, some of which are reminiscent of those usually only observed in bulk strongly correlated quantum materials. With the recent discovery of van der Waals $f$-electron materials, the design of novel MSLs of intrinsic strong correlation is now within the reach. Here we study the novel electron phases of two-dimensional heavy-fermion MSL with increasingly diluted $f$-electron local moments. By applying dynamical mean-field theory with numerical renormalization group as an impurity solver, we demonstrate the appearance of a different energy scale and a reentrant Kondo breakdown in connection with the emergence of a flat band in the system. We further compare our numerical findings with predictions derived from the Lieb-Mattis theorem and show the necessity of this energy scale to consistently reconcile the predictions with the conventional single-impurity limit for exceedingly large unit cells.