A recently formulated mean-field model of glasses features an equilibrium, zero-temperature Replica-Symmetry-Breaking (RSB) transition in some parameter range. In this range, the model's solution in the Replica-Symmetric phase is expressed in terms of an effective, self-consistent random potential for uncoupled degrees of freedom, where the transition to the RSB phase is characterized by the emergence of spectral-edge localized modes and a pseudogapped quartic vibrational spectrum, resulting in a finite spin-glass susceptibility. These properties are preserved in numerical solutions of the model under nonequilibrium conditions, i.e., upon an instantaneous quench. Inspired by recent advances in computer glasses, we define a micromechanical response function—the linear response to local force monopoles—in the framework of the mean-field model. We establish exact relations between the force monopole stiffness and global susceptibilities, which suggest a close correspondence between the nonequilibrium RSB phase of the model and the above-mentioned effective random potential description. As such, the obtained micromechanical observables constitute a concrete realization of the collective degrees of freedom of the model, offering a bridge between a glassy mean-field model and finite-dimensional glasses. We show that the model's vibrational spectrum can be computed solely from the monopole response statistics and, by employing a marginal stability criterion, we extract a characteristic frequency/stiffness scale of soft glassy modes, which is related to the boson peak in finite-dimensional, laboratory glasses.

Bond disorder in frustrated pyrochlore antiferromagnets can give rise to fundamentally different quantum ground states depending on the nature of the local magnetic moments. Here, we show that the bond-disordered $J_{\mathrm{eff}}=\frac{1}{2}$ pyrochlore antiferromagnet ${\mathrm{NaCdCo}}_2{\mathrm{F}}_7$ realizes an unconventional spin-glass-like state with continued dynamics, in stark contrast to its isostructural $S=\frac{1}{2} {\mathrm{NaCdCu}}_2{\mathrm{F}}_7$ counterpart. High-field magnetization and Co $L_{2,3}$-edge x-ray absorption spectroscopy/x-ray magnetic circular dichroism establish spin-orbit-entangled $J_{\mathrm{eff}}=\frac{1}{2} {\mathrm{Co}}^{2+}$ moments with a substantial unquenched orbital contribution, consistent with local $XY$ anisotropy seen in the isostructural $\mathrm{Na}{A}^{\prime \prime }{\mathrm{Co}}_2{\mathrm{F}}_7$ ($A^{\prime \prime }=\text{Ca}$, Sr) analogs. muon spin relaxation and ${}^{23}\mathrm{Na}$ nuclear magnetic resonsonance (NMR) measurements reveal progressive slowing of spin fluctuations below $\sim 10\mathrm{K}$, culminating in a partially frozen state with persistent low-temperature dynamics that deviates from a canonical spin glass. Comparison with the isostructural bond-disordered pyrochlore ${\mathrm{NaCdCu}}_2{\mathrm{F}}_7$, which realizes a random-singlet state, reveals a fundamentally different response of spin-orbit-entangled ${\mathrm{Co}}^{2+}$ moments to bond disorder. These results identify spin-orbit coupling as a key ingredient governing the fate of bond-disordered frustrated pyrochlore magnets.

A bandwidth-controlled antiferromagnetic Mott-insulating phase in ${\mathrm{Ca}}_3{\left({\mathrm{Ru}}_{1\text{−}x}{\mathrm{Ti}}_x\right)}_2{\mathrm{O}}_7$ is realized through isovalent substitution of the Ru site. For a dilute substitution with only 1% Ti, the Mott insulator ground state remains nearly degenerate with the ground state of pristine ${\mathrm{Ca}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$, where the Ru moments are ferromagnetically aligned within the metallic ${\mathrm{RuO}}_2$ bilayers, which are stacked in an antiferromagnetic fashion. The exceptionally shallow free-energy landscape of this doped compound arises from intertwined electron–electron and electron–lattice interactions. This makes its magnetic and transport properties highly sensitive to external perturbations. We systematically investigated magnetic-field-induced phase switching in ${\mathrm{Ca}}_3{\left({\mathrm{Ru}}_{0.99}{\mathrm{Ti}}_{0.01}\right)}_2{\mathrm{O}}_7$ to explore its magnetic $H\text{−}T$ phase diagram. With the field applied along the easy $b$ axis, parallel to the antiferromagnetic moments, the magnetization exhibits a first-order spin-flop transition at $\approx 6\mathrm{T}$, indicating reorientation of the $\mathrm{Ru}$ moments perpendicular to the field. The transition is accompanied by a decrease in the electrical resistance, but the spin-flop phase remains insulating. Above $10.5\mathrm{T}$, all Ru moments align with the $b$ axis, resulting in a forced ferromagnetic metallic phase. In contrast, neither spin-flop nor forced ferromagnetic phases are observed up to $14\mathrm{T}$ when the field is applied along the $a$ axis. While the electronic kinetic energy and the electron–lattice coupling contribute to the free-energy balance of this system, the resulting $H\text{−}T$ phase diagram is remarkably simple and closely resembles that of a canonical anisotropic antiferromagnet, albeit with substantially renormalized critical fields.

We studied acoustoelectric (AE) currents in materials that undergo charge density wave (CDW) transitions, induced by a surface acoustic wave (SAW) on a piezoelectric substrate. The polarity and magnitude of the AE current in ${\mathrm{NbSe}}_3$ and $2H\text{−}{\mathrm{TaSe}}_2$ were modulated due to their CDW transitions. We also found that the sign of the AE current depends on the SAW propagation direction with respect to the crystalline axis of the substrate. A phenomenological model assuming strain-modified conductivity can qualitatively account for the significant modulation of the AE current associated with the CDW transition, as well as the SAW propagation orientation dependence. The present results offer a powerful probe for exploring SAW-electron interactions in van der Waals materials, thereby highlighting their potential for advancing the emerging field of straintronics.

In this work, we investigate dielectric materials for thermoreflectance-based thermal sensing by extracting key optical parameters using temperature-dependent spectroscopic ellipsometry in the midinfrared regime. Leveraging optical phonon resonances, we demonstrate that the thermoreflectance coefficients in infrared-active polar dielectrics rival, and in some cases exceed by an order of magnitude, those observed in commonly used metals that are typically used as temperature transducers in thermoreflectance measurements. We introduce a transducer figure of merit (FOM) that combines pump absorption and probe reflectance modulation at different wavelengths, serving as a design-oriented screening metric for comparing thermoreflectance transducer performance across materials and spectral regions. Our results show that polar materials can exhibit material-level FOM values up to eight times those of metal transducers. To demonstrate practical capability, we perform transient thermoreflectance measurements on a 100-nm thermally grown ${\mathrm{SiO}}_2$ film on silicon. These results position dielectric materials as compelling candidates for next-generation thermal metrology, broadening the design space for optical thermometry, with strong implications for high-resolution thermal mapping and characterization of layered device structures based on phonon probing.

Thouless pumping is a transport phenomenon whereby an insulating, time-periodic Hamiltonian induces a robustly quantized transfer of charge, per driving cycle, in the quasiadiabatic limit. In this work, we apply the shortcuts to adiabaticity method of counterdiabatic (CD) driving to the Rice-Mele model, an archetypal model for Thouless pumping. We show that the charge pumped rapidly across each bond of our CD Rice-Mele model is robustly quantized and determined by a Chern number. The CD Hamiltonian generally involves long-range, hence nonlocal, hopping. Therefore we also derive an exact, local, nearest-neighbor CD Hamiltonian for our lattice system. We show that our nearest-neighbor nonadiabatic protocol possesses the same topological robustness to on-site disorder as quasiadiabatic Thouless pumps and is moreover surprisingly robust to on-site disorder and noise errors in implementing the CD protocol for sufficiently rapid driving. The protocol also reproduces finite-temperature Thouless pump results away from the adiabatic limit. In addition, we develop a general method to produce nontrivial, finite-time quantized pumping starting from any Rice-Mele initial ground state using only nearest-neighbor hopping.

Magic-angle twisted bilayer graphene (MATBG) hosts narrow moiré bands with meV-scale dispersion and energy splittings, making its correlated phases sensitive to both material parameters and modeling choices in low-energy downfolding. We develop an ab initio quantum-embedding workflow that derives interacting flat-band Hamiltonians from Kohn-Sham density functional theory (KS-DFT) of a relaxed, unstrained structure. Our model combines constrained random phase approximation screening, controlled double-counting subtraction, and an automated gauge-fixing procedure based on the selected columns of the density matrix that is compatible with symmetry-resolved many-body calculations. Solving the resulting models using Hartree-Fock and coupled cluster singles and doubles, we recover robust insulating Kramers intervalley coherent states at charge neutrality ($\nu =0$) and at electron doping ($\nu =+2$). The main unique physical effect appears on the hole-doped side: At $\nu =-2$, we observe a fragile semimetal with a weak $\sqrt{3}\times \sqrt{3}$ Kekulé modulation and enhanced intervalley-scattering peaks in the Fourier-transformed local density of states. Although the underlying KS-DFT band structure is nearly particle-hole symmetric, the effective interacting Hamiltonian exhibits a pronounced particle-hole asymmetry at $\nu =\pm 2$ that we trace to momentum-dependent single-particle renormalizations generated by subtraction terms constructed from reference densities consistent with the KS-DFT filling. Our work provides a first-principles route for connecting microscopic electronic structure, screened interactions, subtraction choices, and scanning tunneling microscopy signatures in MATBG.

Scanning superconducting quantum interference device imaging of ${\mathrm{CaSb}}_2$ reveals dense vortex clusters with enhanced boundary susceptibility and suppressed internal vortex motion, features that are inconsistent with both isolated-vortex and flux tube behaviors. These measurements provide a local visualization of magnetic dynamics within vortex clusters in a weakly pinned superconductor, offering an alternative route to probe nonmonotonic vortex-vortex interactions that are typically expected in single-band type-II/1 or multiband type-1.5 superconductors. Although the superfluid density follows a single-gap BCS model, vortex clustering and spatially inhomogeneous dynamics are clearly observed in a regime where reported Ginzburg-Landau parameters place ${\mathrm{CaSb}}_2$ near the type-I/type-II boundary.

We demonstrate that the recent observations of spatial oscillations in the energy position of the superconducting coherence peaks in the cuprate, transition metal dichalcogenide, iron-based, and heavy-fermion superconductors are consistent with the possible presence of a pair-, charge-, or spin-density-wave phase. We show that for all three cases, the spatial oscillations of the superconducting order parameter, $\mathrm{\Delta }\left(\mathbf{r}\right)$ can be imaged via the critical Josephson current, $I_c\left(\mathbf{r}\right)$ measured in Josephson scanning tunneling spectroscopy experiments. Finally, we show that the spatial oscillations of the density waves and of $\mathrm{\Delta }\left(\mathbf{r}\right)$ exhibit relative phase shifts of $\mathrm{\Delta }\varphi =0$ or $\pi$ for a charge-density wave, and $\mathrm{\Delta }\varphi =\pi /2$ for the spin-density wave.

Superconducting weak-link junctions host electron-hole hybridized excitations called Andreev bound states, central to mesoscopic transport and emerging quantum information platforms. Andreev physics has so far been synonymous with the microwave range. However, advancements in superconductor-semiconductor hybrid junctions open the door to the characterization, and manipulation, of Andreev states by light. Here we introduce a model for light-Andreev interaction, with distinct features: Electrons transitioning into Andreev levels can sidestep Pauli exclusion, resulting in two optical absorption resonances separated by twice the bound-state energy. One resonance populates the Andreev state and the other empties it, enabling optical control of Andreev qubit parity; pumping both resets the junction and prevents saturation. Given their strong microwave coupling, we show how Andreev bound states can operate as optical-to-microwave transducers with MHz-scale intermode coupling, a key ingredient for heat load management and quantum networking. We illustrate these effects with realistic device parameters. Our results highlight the possibilities in the new field of Andreev optoelectronics.

We investigate the spin dynamics of the cuprate ladder ${\mathrm{Sr}}_{2.5}{\mathrm{Ca}}_{11.5}{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ to elucidate the behavior of its intrinsically doped holes. By combining high-resolution inelastic neutron spectroscopy with density-matrix renormalization group calculations, we obtain a detailed and quantitative description of its collective magnetic excitations within a single-band framework. Remarkably, we observe an absence of magnetic signatures associated with unpaired charges, suggesting that the doped holes form strongly bound, localized Cooper pairs. Indeed, while the standard single-band Hubbard model fails to reproduce the observed excitation spectrum, a minimal extension incorporating a strong attractive nearest-neighbor interaction quantitatively accounts for the experimental results. Our findings underscore the necessity of including interactions beyond conventional magnetic mechanisms in driving charge pairing when the system is modeled using the single-band Hubbard model. Given the close correspondence between ladder systems and two-dimensional cuprates, these results may have important implications for pairing phenomena in square-lattice cuprate materials.

The Migdal-Eliashberg theory (MET) describes electrons interacting with phonons in the adiabatic limit when the phonon Debye frequency is much smaller than the Fermi energy. A conventional belief is that MET holds even at strong coupling, when electron self-energy is large, and for an interaction with an optical phonon breaks down only near the point where the dressed phonon spectrum softens to near zero. We analyze numerically and analytically a different option for this case—a collapse to a polaronic/bipolaronic ground state. The last scenario has never been analyzed in precise quantitative terms for a generic electron density. Using variational considerations, we establish rigorous upper bounds on the coupling $\lambda$, at which a Fermi-liquid state transforms into the bipolaron/polaron state. We show that at small and near-maximum densities, this happens well before a dressed phonon softens. This is true both in two- and three-dimensional systems; in the latter, the upper bound on $\lambda$ tends to zero in the limit of small or near-full density. We present analytical reasoning for this behavior based on hints extracted from exact diagrammatic treatment of the on-site Holstein model for the spin polarized case and argue that polarons are produced by fermions with energies comparable to the bandwidth; i.e., polaron formation is outside the realm of MET. Closer to half-filling, the leading instability upon increasing $\lambda$ is toward a charge-density-wave state (CDW), and there exists a strong coupling regime of MET near this instability, while the polaron/bipolaron state develops at larger $\lambda$ out of a CDW-ordered state and inherits a CDW order over some range of coupling.

By forming hybrid light-matter states, optical cavities offer a route for engineering material properties, however, unambiguously probing the effects of light-matter coupling remains difficult. Here, we show that the polarization-resolved statistics of photons transmitted through a cavity, measurable via $g^{\left(2\right)}$, provide one such diagnostic. By relating $g^{\left(2\right)}$ to matter correlation functions such as the Raman structure factor, we link photon bunching and antibunching to material properties. By applying this method to the stripy-to-antiferromagnetic transition in the Kitaev-Heisenberg spin model, we find that polarization-dependent patterns of bunching and antibunching encode the magnetic point-group symmetries of each phase and characterize the behavior at the phase boundary. Finally, we predict measuring $g^{\left(2\right)}$ for output photon pairs polarized orthogonal to the input field will isolate higher-order light-matter scattering processes that probe higher-order material correlations.

Controlling hot-carrier relaxation in quantum-confined semiconductors remains a fundamental challenge in nonequilibrium condensed-matter physics. Here, we report for the first time that assembling colloidal quantum dots into a quantum dot solid (QDSolid) dramatically suppresses hot-carrier cooling by inducing transient localization in high-lying continuum states. Ultrafast transient-absorption spectroscopy reveals that carriers injected $\sim 1.2\text{eV}$ above the band edge in QDSolid remain localized for at least an order of magnitude longer than in uncoupled quantum dots. This localized population produces correlated high-energy photobleach and broadband photoinduced absorption features, observed universally across QDSolids of different sizes and compositions. First-principles density functional theory calculations attribute this phenomenon to the intrinsic positional disorder in the QDSolid, which generates local potential fluctuations that trap hot carriers. Our results demonstrate that positional disorder, often considered a limitation, can be harnessed to engineer localized carrier populations in extended quantum systems.

In an ultrafast optical-pump terahertz-probe measurement, the photoinduced material response can be modulated on a timescale shorter than the extent of the THz pulse. In this situation, the measured time-frequency response deviates from a simple time-dependent linear response. When full two-dimensional time-frequency maps are measured, oscillatory artifacts persisting after pump-probe overlap can be incorrectly assigned to a photoexcited coherent response. We investigate this experimentally via the measured response of photoexcited SnSe, whereby photoinduced phase change dynamics lead to ultrafast changes of the charge carrier and lattice optical conductivity. Two-dimensional time-frequency THz transmission maps subsequently show unexpected time-frequency features at early pump-probe delay times. These features are reproduced in both finite-difference time-domain simulations of the THz experiment and in an extension of non-equilibrium response function theory, demonstrating their systematic origin.

The microsopic origin of the charge-density wave (CDW) in $A{\mathrm{V}}_3{\mathrm{Sb}}_5$ ($A$ = K, Rb, Cs) kagome metals remains a longstanding question, often revolving around electron-phonon coupling and purely electronic mechanisms involving Van Hove scenarios, nesting, and sublattice interference. To reveal the processes driving the CDW transition, we combine ab initio calculations analysis of the phonon self-energy and ARPES. Our momentum-resolved study, supported by ARPES data, reveals that lattice instabilities in the V-135 family of kagome metals appear to also be driven by electronic states far from high-symmetry points, where these states exhibit the strongest coupling with the phonon modes responsible for the CDW distortion. Footing on an interpretation scheme based on phonon fluctuation diagnostics, our work challenges and revises theories that so far have exclusively attributed CDW formation to nesting effects close to the Fermi level.

We report a comprehensive muon spin relaxation (${\mu }^{+}\mathrm{SR}$) and bulk magnetization study of the antiferromagnetic (AFM) Weyl semimetal ${\mathrm{Mn}}_3\mathrm{Sn}$ (composition ${\mathrm{Mn}}_{2.99}\mathrm{Sn}$). ${\mathrm{Mn}}_3\mathrm{Sn}$ is reported to exhibit a commensurate inverse triangular (IT) AFM phase, an incommensurate (IC) helical AFM phase, and a proposed low-temperature spin-glass-like state. In our sample, we identify the characteristic temperatures associated with these regimes as Néel temperature ($T_{\mathrm{N}}=418\mathrm{K}$), a macroscopic bulk transition temperature between IT-AFM to IC helical phase ($T_{\mathrm{t}}\approx 275\mathrm{K}$), and low-temperature transition $T_{\mathrm{f}}=21\mathrm{K}$. Investigating the low-temperature regime below $T_{\mathrm{f}}$, we find no evidence of a static spin-glass state. Instead, the sample exhibits an increasing ferromagnetic component accompanied by a localized slowing of spin fluctuations, indicating that these phenomena may be decoupled. In the IC helical AFM phase, the zero-field spectra are best described by damped oscillations with an empirical phase offset, consistent with anharmonic and amplitude-modulated order reported by scattering studies. Upon warming above 150 K, a continuous redistribution of muon spectral weight reveals a broad, homogeneous magnetic crossover between the IC helical and IT-AFM phases. In the commensurate IT-AFM phase above $T_{\mathrm{t}}$, a persistent missing fraction in the initial asymmetry indicates that a subset of implanted muons, corresponding to roughly 20% of the sample-related asymmetry, undergoes unresolved ultrafast depolarization. Finally, we observe temperature-driven shifts in muon site populations above 325 K. Ultimately, our results show a highly dynamic magnetic landscape in ${\mathrm{Mn}}_3\mathrm{Sn}$, demonstrating how its complex magnetic orders often coexist and evolve continuously with temperature.

We report diffuse scattering measurements on the dipolar-octupolar pyrochlore ${\mathrm{Ce}}_2{\mathrm{Sn}}_2{\mathrm{O}}_7$ to elucidate its magnetic correlations within the correlated paramagnetic regime above its ordering temperature $T_N\sim 40\text{mK}$. The magnetic transition at $T_N$, observed in recent specific heat measurements, has been interpreted within the nearest-neighbor XYZ model as a transition into an all-in-all-out (AIAO) magnetic order. However, the observed diffuse scattering above $T_N$ argues against an AIAO magnetic order by exhibiting no short-range order at the AIAO wave vectors, inconsistent with the nearest-neighbor model. Instead, the observed diffuse scattering strongly resembles that observed in classical dipolar spin ice, ${\mathrm{Dy}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$, and suggests the presence of short-range correlated structures such as chains or clusters in the low-energy manifold of ${\mathrm{Ce}}_2{\mathrm{Sn}}_2{\mathrm{O}}_7$, favored by further neighbor interactions. We discuss how chainlike states qualitatively account for the observed H-T phase diagram under a [1,1,0] field.

Recently, ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ thin film on the ${\mathrm{LaAlO}}_3$ substrate is shown to be superconducting, while the bulk ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ with the same in-plane lattice constant under pressure does not superconduct. This difference suggests the interlayer distance $d_{\mathrm{Ni}-\mathrm{Ni}}$ is crucial to control superconductivity, and its variation under pressure may tune the ground state sensitively. We investigate systematically the ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7/{\mathrm{LaAlO}}_3$ thin films in a reasonable range of $d_{\mathrm{Ni}-\mathrm{Ni}}$, by a combination of the first-principle calculations and the singular-mode functional renormalization group. For smaller (larger) $d_{\mathrm{Ni}-\mathrm{Ni}}$, the ground state is a C-type (G-type) spin density wave with spins coupled ferromagnetically (antiferromagnetically) across the two layers. Between the two phases, $s_{\pm }$-wave superconductivity emerges with dominant pairings between nickel $3d_{3z^2-r^2}$ orbitals. The results explain the experimental superconductivity in the thin film under ambient pressure, and predicts that the applied pressure will decrease the superconducting transition temperature, until the system enters the C-type spin density wave. Experimental verification would provide profound insights into the nature of electron correlations in this system, since the C-type spin density wave is achieved most naturally in the itinerant picture, while it would be hard in the local moment picture where spins are always coupled antiferromagnetically across the layers.

We report nonlinear differential-resistance measurements in a high-mobility GaAs/AlGaAs two-dimensional electron system patterned in a Corbino geometry. At zero magnetic field, $R_{\mathrm{diff}}\left(I_{\mathrm{dc}}\right)$ exhibits a pronounced polarity-selective threshold peak on the negative-current branch, gradually suppressed by a perpendicular magnetic field. We interpret the Corbino anomaly as a local Cherenkov-like threshold for acoustic phonon emission, enabled by the radial current concentration $j_r\left(r\right)=I/\left(2\pi r\right)$, which drives the local electron velocity above the sound velocity in a region adjacent to the inner contact. The polarity selectivity is attributed to Peltier heating and cooling, which modify the local thermal and boundary conditions near the contact, rather than to the kinematic threshold itself. Our results identify the Corbino geometry as a sensitive platform for probing local nonequilibrium electron-phonon processes in a high-mobility electron system within an independently established hydrodynamic-crossover regime, and they suggest that the inner Corbino contact can act as a geometry-defined source for supersonic acoustic emission.