Papers

Understanding how frustration and symmetry breaking shape collective behavior is a central problem in quantum many-body systems. In this work, we investigate this problem in large one- and two-dimensional arrays of coupled Dicke models on a periodic lattice, where strong light-matter coupling gives rise to a superradiant phase and competition between neighboring order parameters induces spontaneous translational symmetry breaking. Such Dicke lattice models constitute a fundamentally new class of quantum many-body systems, as they simultaneously realize the thermodynamic limit associated with the lattice size and an intrinsic thermodynamic limit arising from collective on-site interactions with quantum emitters. We show that frustration drives photonic density-wave ordering, and that the resulting broken periodicity can be predicted from the excitation spectrum of the symmetric phase, without requiring computationally prohibitive thermodynamic energy minimization. Furthermore, we demonstrate that an emergent Nambu-Goldstone mode arises near the critical point in a one-dimensional chain despite the presence of only discrete symmetry, and uncover the mechanism that enables this otherwise forbidden gapless excitation. We also find quasi-periodic ordering in the superradiant phase, reminiscent of quasicrystals, and demonstrate that synthetic magnetic flux provides a powerful knob to control the nature of translational symmetry breaking. Our results establish a new direction in quantum many-body physics where the coexistence of local and global thermodynamic limits gives rise to unconventional symmetry breaking and emergent collective behavior.

We present a combined theoretical and experimental study of ground and excited Rydberg exciton states in wide GaAs quantum wells exposed to a magnetic field in the Faraday geometry. We employ a multiband exciton model based on the Luttinger Hamiltonian, which captures valence-band mixing between heavy- and light-hole states induced by both the quantum well confinement and the magnetic field, and we develop an efficient numerical approach to solve for both ground- and excited-state excitons. The method treats Coulomb interactions, magnetic confinement, and band mixing on an equal footing, enabling a systematic characterization of exciton energies, oscillator strengths, and orbital composition. We show that band hybridization increases with magnetic field and is significantly more pronounced for higher excited states, where it sets in at lower fields and strongly modifies their properties. The theoretical predictions are validated by polarization-resolved magneto-reflectance measurements up to 9 T on GaAs/Al$_{0.4}$Ga$_{0.6}$As quantum wells of 20 nm width. We find excellent agreement for both the diamagnetic shift and Zeeman splitting of the ground state and the first four Rydberg excitons. Our results demonstrate that valence-band mixing plays a crucial role in determining the magnetic-field dependence of excited exciton states and must be properly included for a quantitative description of magneto-excitons in wide GaAs quantum wells.

We investigate the thermodynamic meaning of the dissipation potential in Nambu nonequilibrium thermodynamics (NNET) using a simple open-piston model. The system is described by three variables: the gas volume, the piston momentum, and the thermodynamic entropy of the gas. The reversible dynamics is formulated in terms of two Nambu Hamiltonians, the extended energy and the thermodynamic entropy, while the irreversible dynamics is generated by a bath-relative Massieu-type dissipation potential through a positive-semidefinite gradient flow. This construction reproduces the physical processes of frictional heating and heat exchange with the reservoir while preserving their thermodynamic interpretation. We show that the time derivative of the dissipation potential coincides with the total entropy production rate of the system and the heat bath. Although the subsystem entropy may evolve nonmonotonically, the dissipation potential is a Lyapunov function under the conditions realized in this model. These results provide an explicit thermodynamic interpretation of the dissipation potential and its associated Lyapunov structure within NNET.

We propose a Floquet-engineered cold atom realization of a parity anomaly inspired anomalous Hall staircase in a two dimensional $\pi$-flux lattice. The effective model hosts massive Dirac fermions generated by the combined action of a time reversal symmetry breaking Floquet mass and a static inversion breaking mass offset. An additional momentum dependent scalar displacement term shifts different Dirac sectors in opposite energy directions without modifying their Bloch eigenvectors. As a result, the Berry curvature contribution associated with individual massive Dirac sectors can be selectively occupied, allowing the anomalous Hall response to evolve stepwise as a function of chemical potential or scalar displacement term. Evaluating the full lattice Berry curvature integral, we find plateau-like responses near $0$, $e^2/2h$, and $e^2/h$, corresponding respectively to the activation of zero, one, and two effective massive Dirac sector contributions. We analyze the associated low energy Dirac theory, band topology, Berry curvature structure, and two parameter response maps, and discuss a possible realization using Raman-assisted tunneling, off-resonant Floquet driving, and auxiliary AC-Stark dressing in ultracold atomic optical lattices.

Spatially embedded networks are central to many physical and biological systems, where geometry and connectivity jointly shape structure and function. Examples abound across the scales of biological organization, from network-like membrane-bound organelles in the cell to mesoscale tissue organization of multiple distinct flow networks in organs and beyond. In each of these cases, the complexity of the architectures has heretofore frustrated our ability to link mechanism or regulation of these structures to reduced modeling or even relevant characterization, putting structure-function relationships largely out of reach. Complex, functional spatial networks can be decomposed into tree-like and cyclic substructures, but we still lack both an understanding of how these elements intertwine to give rise to function, and the tools to holistically quantify both the topological and geometric aspects of these features in their full network context. To close this gap, we here introduce GEMINI, a topology and geometry aware operator that directly characterizes incomplete linking and more general spatial associations between edges in spatially embedded network architectures. GEMINI contains information on edge-edge association through an incomplete version of the Gauss linking integral which simultaneously endows it with topological sensitivity when collections of edges form linked assemblages. Validation on both synthetic lattices and on mouse brain vasculature data demonstrates that GEMINI systematically captures and classifies the complexity of structural organizations. Our results provide a general approach for analyzing spatial networks in realistic data, where topology and geometry together determine function, thus opening the door to a more complete understanding of structure-function relationships across a broad set of biological examples where complex network organization is key.

Accurate electronic excited states are essential for photochemistry, spectroscopy and non-adiabatic molecular dynamics, but high-level calculations often scale steeply and require prior knowledge of the target state's character or symmetry. Here we show that variational excited-state optimization can be reformulated as an iterated ground-state-like problem for a low-energy subspace of the electronic Hamiltonian. Applying this variational principle to non-orthogonal Slater determinants leads to EXIDOS, an automatic method for excited state calculations controlled only by the number of states and determinants per state. EXIDOS optimizes multiple excited states simultaneously, without explicit orthogonality constraints or imposed spin and point-group symmetries. Benchmarks against FCI and state-of-the-art quantum chemistry methods show chemical accuracy for a multitude of states in N$_2$ and CO, charge-transfer states in HCl, Rydberg states in NH$_3$, double excitations and extended potential-energy curves in C$_2$, and avoided crossings and conical intersections in ethylene. These results establish EXIDOS as a low-scaling, fully variational route to chemically accurate excited states.

Atom probe tomography (APT) of organic molecular liquids is limited by poorly reproducible specimen geometry, reduced milling rates, and beam sensitivity during cryo-FIB preparation. Here we introduce a MicroCup strategy that confines liquids in a FIB-prepared nanoscale cavity prior to phase separation, reduces deposited volume to increase preparation throughput, enables reproducible specimen geometry, and minimizes beam exposure in the region of interest. Using the liquid crystals 4'-octyl-4-cyanobiphenyl (8CB) and 4'-octyloxy-4-cyanobiphenyl (8OCB) as model systems, we establish stable and reproducible field evaporation conditions, enabling the detected intact ion molecular preservation above 70% in smectic-like phases with interpretable fragmentation behavior. Comparative analysis further shows that the oxygen atom in 8OCB promotes preferential cleavage pathways associated with bond polarization under high electric fields. By inducing partial crystallization within the MicroCup cavity, distinct regions could be resolved: 8CB shows broadly similar evaporation behavior across crystalline and amorphous regions, whereas 8OCB exhibits clearer regional contrast, with smectic-like regions dominated by intact molecular or large fragments and crystalline domains producing small alkyl fragments and ether-type species. These results provide spatially resolved evidence of a solid-liquid interface in a freeze-prepared organic liquid by APT and establish a reproducible workflow for probing local phase behavior in soft materials.

Accessing surface quantum transport in topological insulators is hampered by residual bulk conduction arising from lattice defects. Here, we demonstrate a novel synthesis pathway for realizing high mobility $\beta$-Ag$_2$Te thin films where surface transport is dominant. An in-situ vacancy engineering step as part of the molecular beam epitaxy growth process acts to modify the stoichiometry and suppress donor-type defects, enabling continuous tuning of the sheet carrier density over more than an order of magnitude through the charge-neutrality point without an external gate electrode. In the lower-carrier-density films, a fully developed $\nu=1$ quantum Hall state is observed, and Landau-level energies extracted across samples collapse onto the $E_N=v_\mathrm{F}\sqrt{2e\hbar NB}$ relation, providing evidence for the massless Dirac dispersion of the top and bottom surface states. These results establish stoichiometry-driven vacancy engineering as a versatile lithography- and gate-free approach to accessing quantum Hall transport in epitaxial topological-insulator thin films.

When a quantum system passes through an unstable fixed point the local dynamics reduces to the inverted harmonic oscillator (IHO). It exponentially amplifies along one quadrature while squeezing the other, producing macroscopically extended quantum states from microscopic zero-point fluctuations. We realize this dynamics with a Bose-Einstein condensate on an AtomChip. Radio-frequency dressing flips the transverse harmonic confinement into an IHO. Through phase-space tomography we follow the full Wigner function of the evolving quantum state, observe sub-vacuum squeezing of 10.6(1.3) dB, and test coherent reversibility by time-reversing the IHO evolution. Matter-wave interference between the two daughter clouds confirms quantum coherence over timescales far beyond the initial expansion. Our experiment establishes ultra-cold atoms as a clean, controlled, many-body platform for unstable quantum dynamics opening a route to force sensing with time-reversal-based coherence certification and to analog studies of the amplification of quantum fluctuations in inflationary field dynamics.

An ab initio framework using density-functional theory has been developed to predict hydrogen solubility in both pristine and defective e̱ta}-SiC. This study is motivated by the critical need for accurate hydrogen permeation models in fusion reactor designs, where predicting hydrogen permeation through tritium permeation barrier (TPB) materials is essential. Although silicon carbide is one of the leading candidates for TPBs, experimental permeation values vary widely due to differences between ideal single crystals and real, defect-containing materials. First principles calculations are employed to quantify the effects of interstitials, vacancies, and nonstoichiometric (amorphous) structures on hydrogen behavior in e̱ta}-SiC. Our results show that hydrogen solubility is significantly enhanced in carbon-rich nonstoichiometric amorphous structures and silicon vacancies compared to hydrogen occupying interstitial sites in pure e̱ta}-SiC.

A strongly interacting chain of Majorana fermions realizes the supersymmetric tricritical Ising phase, with supersymmetry (SUSY) extending into a symmetry-broken ordered phase adjacent to the tricritical point. Although the signatures of SUSY at the tricritical point are well understood, their behavior in the gapped phase remains less clear. Here, we address two key questions: how SUSY manifests in the gapped phase and what is the nature of the excitations in this phase. We show that, in the thermodynamic limit, a conventional SUSY diagnostic that remains finite at the tricritical point diverges immediately on the Ising side, yet decays continuously to zero deeper in the gapped phase, signaling the persistence of SUSY. Focusing on the lowest excited states in the supersymmetric gapped regime, we find that the excitations consist of soliton-antisoliton pairs separating distinct ordered regions. Each soliton binds an emergent localized Majorana mode, and together the pair forms a nonlocal Dirac fermion. The occupation of this Dirac mode distinguishes eigenstates with even and odd fermion parity.

Valley-polarized excitons in two-dimensional transition metal dichalcogenides (TMDs) offer a promising platform for quantum applications, yet the addressability and decoherence of these states remain fundamental challenges. Here, by developing a first-principles electrostatic embedding approach and performing large-scale GW plus Bethe-Salpeter equation calculations, we reveal novel excitons that emerge in TMD monolayers when supported by a ferroelectric twisted bilayer hBN substrate. We predict two competing low-energy excitons whose ordering depends on the dielectric environment: optically dark, charge-transfer excitons, and quasi-one-dimensional Wannier excitons with linear optical dichroism. The spatial localization of Wannier excitons, together with intervalley exchange interactions in monolayer TMDs, splits valley-degenerate excitons by about 3~meV without external magnetic fields. Our ab initio calculations clarify the role of the interfacial twist angle and the spatial localization of fringe fields, establishing design rules for engineering long-lived two-level systems in TMD monolayers supported by ferroelectric substrates.

Light-induced superconducting-like states have been reported in several classes of correlated materials. From a theoretical point of view, the induction of $\eta$-pairing is a promising route to nonthermal superconductivity. Numerical studies of photo-doped Mott systems revealed $\eta$-pairing states with very high effective critical temperatures. These investigations were however restricted to particle-hole symmetric states in large-gap Mott insulators, while the experiments were performed on strongly correlated metallic systems. It is thus relevant to explore if $\eta$-pairing also exists in non-particle-hole symmetric setups and in photo-excited metallic states. Here we use steady-state nonequilibrium dynamical mean field theory combined with a strong-coupling impurity solver up to third order to investigate this issue. We find that in the strongly correlated regime with large Mott gap, and for low effective doublon and holon temperatures, $\eta$-pairing is robust against changes in the total filling and an imbalance in the doublon and holon density. An asymmetry in the effective doublon and holon temperatures can however strongly suppress the order parameter. In photo-doped metallic systems with a three-peak structure in the local density of states, $\eta$-pairing can be realized in set-ups with positive doublon and holon temperatures and a population inversion in the low-energy quasi-particle band.

In this exploratory work, we aim to understand the mechanoluminescence (ML) phenomenon manifested by various inorganic compounds by focusing on the influence of mechanical loading on local distortion and loss of symmetry at active sites. To this end, we have analyzed the elastic deformation of several relevant crystalline phases and shown, through a kinematic analysis based on elastic constants, that the loading-induced distortion is smaller than, but remains comparable in magnitude to, the intrinsic structural distortion as quantified by the Baur descriptor. Although the structural distortion has previously been proposed as a structural fingerprint of the ML potential of a compound, it is by nature a static parameter, and must be supplemented by a dynamic distortion contribution that develops under mechanical load. By approximating the crystal deformation by that of simple polygonal motifs, we have been able to propose a rationale for otherwise puzzling observations: in particular, the marked differences in sensitivity to hydrostatic pressure and to shear, the appearance of an intense ML peak upon unloading in certain compounds, and the contrast in behavior depending on whether the preliminary UV irradiation is performed under load or at rest.

In thin layers of the 2D magnetic semiconductor CrSBr, very recent studies identified two distinct band-edge optical resonances, believed to arise from distinguishable bulk and surface excitons. This behavior reportedly originates from the highly anisotropic nature of CrSBr – particularly in its antiferromagnetic state – where excitons are effectively confined within individual monolayers, such that excitons in the two surface layers "see" a different local dielectric environment and have a lower resonance energy. To explore this scenario, here we investigate optical absorption properties of few-layer CrSBr in magnetic fields. In addition to the fundamental exciton resonance at ~1.36eV, we observe an absorption resonance ~20 meV lower in energy. Compared to the fundamental transition, this resonance redshifts only half as much in small magnetic fields that induce ferromagnetic order, while in high fields to 55T it exhibits a smaller diamagnetic shift. Both behaviors point to distinguishable populations of bulk and surface excitons in CrSBr.

Theoretical heterogeneous catalysis promises rapid catalyst discovery, yet computational and machine-learning predictions often deviate from experiment and stay confined to narrow material families, for want of a faithful, condition-aware catalytic simulator. We present CatDT (Catalysis Digital Twin), a self-evolving multi-agent system that builds an autonomous digital twin of a working catalyst, unifying gas-solid and liquid-solid modeling. From only a bulk crystal and a natural-language reaction description, eight specialized agents and 27 scientific tools predict stable facets, reconstruct working surfaces, enumerate and rank reaction pathways, locate transition states, and compute kinetics in 5-30 min on a single GPU. Two innovations address the hardest steps: UniMech finds dominant pathways for novel materials at over $10^3\times$ lower cost than exhaustive enumeration by fusing agent-guided proposals with energy-cached graph search, and a memory-augmented reinforcement loop raises barrier-calculation success from 41% to 84% across 600 catalytic surfaces. Across seven gas-solid benchmarks – stepped metals, single-atom catalysts, ordered intermetallics, vacancy-rich 2D sulfides and carbides, and a strong-metal–support-interaction (SMSI) interface – every CatDT prediction lies within 0.5-2 times experiment over four orders of magnitude. For propane dehydrogenation, CatDT independently discovers non-precious candidates rivaling the Pt-based industrial benchmark, with a proposed Ni@ZrO$_2$ SMSI overlayer reaching a simulated TOF of $1.63~\text{s}^{-1}$ at $\sim$100% selectivity. More broadly, the decisive factor for a faithful catalyst digital twin – or any multi-stage scientific simulator – is not raw LLM capability but the engineered harness around it: deterministic tools, persistent memory, and verified self-improvement that compound across models, tools, and runs.

Stimulated Raman transitions in Faraday geometry allow for simultaneous single-shot qubit readout and qubit control. It involves driving an unbalanced $\Lambda$ system via an auxiliary excited state. Due to the simultaneous driving of both transitions with unequal detuning, the resulting time-dependent Stark shift gives rise to additional resonance conditions beyond the conventional picture. We identify a distinct regime in which repeated passages through avoided crossings lead to step-like population inversion arising from Landau-Zener-Stückelberg interference. By changing the detuning beatnote, we demonstrate a controlled continuous crossover from Rabi-like oscillations to adiabatic population switching. These findings establish the oscillating Stark shift as a mechanism for engineering and controlling spin dynamics in Faraday geometry.

We propose a new quantum simulation method for a many body quantum liquid of identical particles at finite (non-zero) temperature. The new scheme expands the high temperature density matrix on the overcomplete set of single particles coherent states of John Rider Klauder instead of the usual plane waves as in conventional path integral methods. One is free to tune the elastic constant and/or the mass of the harmonic oscillator subtending the coherent states so as to maximize the computational efficiency of the algorithm. We prove that in the limit of an extremely stiff harmonic oscillator the results for the internal energy tends towards the correct expected values. Moreover we suggest that a stiff harmonic oscillator could allow the use of larger (imaginary) timesteps. This additional degree of freedom is the characteristic feature of our new algorithm and is not available in more conventional path integral methods.

We investigate topological electronic responses in a kagome altermagnetic metal hosting a compensated coplanar $120^\circ$ magnetic texture. Using a minimal tight-binding model containing nearest-neighbor hopping, noncollinear exchange coupling, intrinsic spin–orbit coupling, and a time-reversal-odd loop-current order, we disentangle the magnetic, orbital, and relativistic mechanisms governing the electronic response. The exchange field produces pronounced momentum-dependent spin splitting and spin-polarized Fermi surfaces without generating a net magnetization. Nevertheless, in the absence of loop-current order, a hidden antiunitary symmetry $\mathcal{T}C_{2z}$ enforces vanishing Berry curvature and intrinsic anomalous Hall conductivity, even for finite spin–orbit coupling. A directed imaginary bond order breaks this protection and activates finite Berry curvature and a sizable, strongly filling-dependent Hall response already in the nonrelativistic limit. Spin–orbit coupling subsequently reconstructs the avoided crossings and redistributes the Berry curvature, enhancing or suppressing the Hall response depending on filling. For sufficiently strong loop-current order and spin–orbit coupling, a global gap opens at $n_e=3$, and the Hall conductivity approaches $2e^2/h$, consistent with an occupied-band Chern number of magnitude two. Parameter-space and filling-dependent calculations further demonstrate that the Hall-active regime extends over broad ranges of exchange coupling, spin–orbit coupling, and chemical potential and remains robust against symmetry-preserving longer-range hopping. These results identify orbital-current order as an independent route for converting a Hall-silent kagome altermagnet into an anomalous Hall metal or a gapped topological phase without net magnetization, noncoplanar spin order, or scalar spin chirality.

We study the non-equilibrium dynamics of a disordered periodically driven quantum spin chain, with the competition between the interaction, disorder, and Floquet driving being of particular interest. We study dynamics of entanglement entropy, energy absorption to characterize dynamical regimes of the system whether it stays in the Floquet-MBL(many-body localization) region or thermalized region. Starting with a product state in the computational basis, followed by reduced density matrix which in turn gives rise to the entanglement entropy density. With the strength of the interaction, the transverse field, the parallel field, the disorder strength W and the driving frequency, we discover the distinct behaviors of fast delocalization and logarithmic entanglement growth and long-lasting memory of the initial state, indicative of localized or prethermal Floquet regimes. We observe that strong disorder arrests transport and enables slow entanglement dynamics, whereas strong driving frequency arrests energy absorption and creates a long-lived non-equilibrium state. Conversely, weak disorder or low driving frequency leads to delocalization. The outcomes show strong support for non-equilibrium phases in driven many-body systems.

Melting temperature is a critical property for high-temperature materials design, but first-principles melting calculations based on finite-temperature molecular dynamics can require substantial computational resources. The SLUSCHI method reduces this cost by using small-cell solid–liquid coexistence simulations and statistical analysis of many short molecular-dynamics trajectories. Here I present SLUSCHI-UP, a deployed web service for atomistic melting-temperature estimation that couples the SLUSCHI workflow to selectable pretrained universal machine-learning interatomic potentials (uMLIPs) and asynchronous GPU execution. Users submit a crystal structure through a Materials Project identifier or POSCAR input, select a uMLIP backend, and launch a queued melting calculation without local installation of simulation software. The current production interface supports mace-mpa-0-medium, Allegro-OAM-L, and DPA-3.2-5M-OMat24, while beta deployments expose additional models. On the compact MeltBench-10 validation set, the three production backends produce raw coexistence mean absolute errors in the range of approximately 178–327 K. Across the broader set of materials tested so far in MeltBench, the current deployed-job snapshot contains 119 raw uMLIP entries, and PBE-corrected Allegro-OAM-L predictions reach a mean absolute error of approximately 166 K. These values should be interpreted as screening-level infrastructure validation rather than a definitive ranking of uMLIPs. The results demonstrate that SLUSCHI-UP provides a practical, provenance-aware deployment layer between fast scalar melting-temperature predictors and much more expensive first-principles coexistence calculations, while retaining the usual limitations of uMLIP transferability, finite-size sampling, and high-temperature trajectory stability.

We analyze residual frozen flux in a long narrow superconducting strip cooled through its transition temperature $T_{c}$ in a small perpendicular magnetic field. This problem is relevant for the issue of trapped magnetic flux in superconducting electronic devices. During cooling, the low-temperature vortex configuration is formed at temperatures very close to $T_{c}$, where the flux density is determined by dynamic balance between the thermally-activated exits and entries of vortices over the geometrical energy barrier formed by the interaction with the strip edges and the Meissner screening current. In the field range between the minimum flux-expulsion field and the penetration field, the equilibrium flux density is finite due to thermal activation and rapidly decreases with decreasing temperature. During cooling, however, the escape rate decreases exponentially, and the vortex density falls out of equilibrium at a field-dependent freezing temperature $T_{\mathrm{fr}}$. We derive and solve the dynamic-balance equation for this process, which yields definite quantitative results for $T_{\mathrm{fr}}$ and the frozen vortex density. The relative freezing temperature $1\!-\!T_{\mathrm{fr}}/T_{c}$ exceeds the fluctuation width of the transition by a large logarithmic factor, rapidly increases when the magnetic field approaches the minimum flux-expulsion field, and logarithmically increases with decreasing cooling rate. The resulting frozen flux density has a very strong magnetic-field dependence which can be used to define the effective flux-expulsion magnetic field.

Superconductivity mediated by Cooper quartets of charge 4e is a phenomenon of key importance for both the understanding of certain exotic superconductors and the engineering of quantum memories protected at the hardware level by topological order. Josephson junction arrays in the shape of the dice lattice constitute one of the main candidates for the realization of this phase of matter. Here, we analyze numerical signatures of the emergence of this exotic phase when superconducting dice arrays are frustrated by inserting one third of a flux quantum per rhombic plaquette. We adopt simulations of relaxation dynamics to study the critical current of such devices and analyse the Fourier decomposition of their bulk supercurrents. A further characterization of these systems at finite temperature is obtained through Monte Carlo techniques and two-dimensional infinite tensor networks. Our results indicate that the observed peaks of the critical current and temperature at frustration 1/3 correspond to a superconductor-insulator phase transition compatible with the deconfinement of half-vortices, while the low-temperature correlation functions of the model confirm the onset of a 4e superconducting phase mediated by Cooper quartets. We finally address the effects of Josephson energy and flux disorder typical of experimental arrays, and comment on the role of charging energies in the corresponding two-dimensional quantum model.

The technology has been developed for synthesizing Nb$_{1-x}$Sc$_x$ films using magnetron co-sputtering from Nb and Sc targets. The material synthesis was accompanied by structural characterization using X-ray diffraction and X-ray reflectometry methods, which enabled the determination of thickness, phase composition and crystal structure. We also analyzed the superconducting properties. The critical temperature $T_c$ was measured for samples with different concentarions of Sc and Nb. The maximum value of $T_c$ equal to 6.35 K was observed for sample with a scandium content of approximately 15 %, which was determined by Auger spectroscopy. Transport and magnetoresistive measurements were performed in microbridges with length of 50 $\mu$m, width of 2 $\mu$m, and thickness of 30 nm. The critical current density was as high as 2.5 $\text{ MA/cm}^{2}$. Magnetic measurements were performed with the field oriented perpendicular to the sample. The upper critical field $H_{c2}(0) = 3.2$ T, electron diffusion coefficient $D = 1.1$ $\text{cm}^{2}/s$, and coherence length $\xi_{GL} = 10.1$ nm. The synthesized Nb$_{1-x}$Sc$_x$ intermetallic compound shows promise for various functional cryogenic electronics devices. \keywords{NbSc; superconductor; microbridge}

Hydrogenation is an effective strategy for enhancing electron–phonon coupling (EPC) and superconductivity in two-dimensional materials. However, excessively strong EPC can also induce lattice instabilities, leading to charge-density-wave (CDW) formation and structural phase transitions. Here, using first-principles calculations, we investigate CDW order in the Janus transition-metal chalcogenide hydrides 1T-WSH and 1T-WSeH. We find that the high-symmetry phases exhibit pronounced phonon softening at the M point, driving a transition to a commensurate $2\times2$ distorted structure characterized by an emergent triangular charge-density-wave (T-CDW) pattern. Analysis of the electronic structure, susceptibility, and phonon spectrum reveals that the instability is not driven by conventional Fermi-surface nesting but originates from strong momentum-dependent EPC. The T-CDW transition reconstructs the electronic structure and reduces the density of states at the Fermi level, leading to a substantial renormalization of the EPC strength. Consequently, the electron–phonon coupling constants decrease from $\lambda=2.04$ to $1.50$ in 1T-WSH and from $\lambda=3.94$ to $1.06$ in 1T-WSeH, while superconductivity remains robust in CDW phase with predicted transition temperatures of $T_c=12.28$ K and $7.75$ K, respectively. Together with previous results for MoSH and MoSeH, our findings establish a universal mechanism in the 1T-$MCH$ family ($M=\mathrm{Mo},\mathrm{W}$ and $C=\mathrm{S},\mathrm{Se}$), where the primary role of the T-CDW phase is not to eliminate superconductivity but to stabilize the lattice through EPC renormalization. The T-CDW phase therefore acts as an intrinsic self-stabilizing response that relieves excessively strong EPC while preserving phonon-mediated superconductivity.

The interplay between charge-density-wave (CDW) order and superconductivity is a central problem in condensed-matter physics because both phenomena often originate from the same electron-phonon coupling (EPC) mechanism. Here, we investigate the structural, electronic, vibrational, and superconducting properties of monolayer W2N and halogen-functionalized W2N (W2NF2 and W2NCl2) using first-principles calculations. Pristine W2N exhibits pronounced phonon instabilities near the M and K points driven by exceptionally strong EPC associated with softened low-frequency phonons. The coincidence between phonon softening and enhanced phonon linewidths identifies the instability as EPC-driven and indicative of a CDW tendency. Inclusion of van der Waals interactions stabilizes the lattice and yields strong-coupling superconductivity with {\lambda} = 1.00 and Tc = 13.2 K, while fluorination further weakens the soft-phonon anomaly, resulting in a moderate-coupling superconductor with {\lambda} = 0.67 and Tc = 5.3 K. In contrast, W2NCl2 exhibits a re-emergence of CDW-related phonon softening that can be continuously suppressed by compressive strain or electron doping. Under -3% compressive strain, the EPC constant decreases from {\lambda} = 1.35 to {\lambda} = 0.71, giving rise to superconductivity with Tc = 5.8 K. Across the entire W2N family, the low-energy physics is governed by softened ZA phonons near the M point, establishing a unified framework in which CDW order and superconductivity emerge as competing manifestations of the same soft-phonon-driven EPC mechanism.

We investigate the non-equilibrium dynamics of the disordered one-dimensional Fermi-Hubbard model with a focus on many-body localization. The system is initialized in a charge-density-wave-state, and its time evolution is analyzed through sublattice imbalance (spin and charge), and bipartite entanglement entropy. A clear crossover from ergodic to non-ergodic behavior is observed with increasing disorder strength. In the weak disorder regime, rapid decay of imbalance and the fast growth of entanglement indicate efficient thermalization. In contrast, a strong disorder leads to persistent imbalance and slow dynamics, signaling the breakdown of ergodicity. The charge and spin sectors exhibit distinct relaxation behavior, providing evidence for partial decoupling between these degrees of freedom. Furthermore, in the interacting regime, the entanglement entropy shows slow logarithmic growth, reflecting the dephasing-driven dynamics characteristic of the many-body localized phase. These results highlight the interplay between disorder and interactions in determining the dynamical properties of the system and establish robust signatures of many-body localization in the Fermi-Hubbard model.

We systematically analyze the stability of the iterative solution of the parquet equations by studying the spectrum of the Jacobian associated with the commonly used damped fixed-point iteration procedure. In this context, we provide an explicit criterion that determines when the physical fixed point of the parquet iteration becomes unstable. Importantly, we demonstrate that misleading convergence issues, observed in parquet calculations at intermediate-to-high interaction values, are not restricted to parameter regions where the two-particle irreducible vertex diverges, but can also arise in absence of vertex divergences. Hence, the misleading convergence issues of parquet-based algorithms are not directly caused by the crossings of two solutions of the (multivalued) Luttinger-Ward functional, that are associated with vertex divergences. Building on these insights, we apply the controlled stabilization strategy of Phys. Rev. Lett. 137, 016502 (2026) to the challenging case of the parquet iteration. This strategy allows the convergence to the physical solution in the instability regimes. We apply this procedure to the zero-point model and the Hubbard model in the atomic limit, where we successfully stabilize the physical solution deep in the non-perturbative regime, even across multiple divergence lines. Further, we compare our stabilization strategy to alternative fixed-point solvers that can be used to solve the parquet problem.

Many-body localization(MBL) provides a mechanism by which isolated interacting quantum systems with disorder can avoid thermalization unlike ergodic systems satisfying the eigenstate thermalization hypothesis(ETH). Many-body localized systems retain signatures of their initial conditions at long times, whereas systems obeying ETH lose such information as they approach thermal equilibrium. Studying Non-equilibrium dynamics across ETH-MBL crossover is an important problem in condensed matter physics. Adiabatic control of parameters in interacting disordered systems provides a powerful framework to investigate MBL phases and their dynamical robustness. Using exact diagonalization and time-dependent numerical methods we study the effects of adiabatically ramped interactions in a disordered spin-1/2 XXZ chain, a paradigmatic model for exploring the many-body localization transition. By monitoring diagonal entropy density and entanglement entropy density growth across various ramp speeds, and system sizes. Our study incorporates Finite-size effects of spectral observables to probe the transition between ergodic and localized phases. The numerical results show that localized dynamical behavior remains largely intact under sufficiently slow ramp evolution, while increasing the driving rate promotes stronger excitation generation and larger entropy growth. This trend highlights the strong dependence of nonequilibrium adiabatic dynamics in disordered interacting quantum many-body systems.

The very strong light-matter coupling regime enables the non-perturbative modification of matter properties via light. Using a patterned GaAs/AlGaAs waveguide with twelve wide quantum wells, we demonstrate hybridization of heavy- and light-hole excitons within a single polariton state and show that, at finite magnetic field, the presence of the light-hole exciton suppresses coupling to the heavy-hole Rydberg excitons and unbound scattering states. We develop a fully microscopic theory that accounts for the combined effects of the magnetic field and light-matter coupling on the excitons, providing an accurate description of the experimental results beyond a perturbative coupled-oscillator framework. This identifies quantum well width as a key control parameter for engineering the light-induced hybridization of matter wave functions in polaritons, which, in turn, can play a crucial role in the optical non-linearities.