ZrTe5, a topological material with tunable quantum phenomena, faces conflicting experimental results largely due to sample quality variations. Despite intense interest in stabilizing its quantum states, a clear strategy for controlling intrinsic defects has remained elusive. Through first-principles investigations of intrinsic point defects, we identify a practical route to achieving stable and ideal topological characteristics in ZrTe5. Our study reveals that donor-like Zr interstitials and acceptor-like Te vacancies compete to govern the Fermi level, with defect density determining topological phases. We theoretically propose increasing the Te/Zr ratio during growth to suppress intrinsic defects, stabilizing ZrTe5 in a nearly ideal weak topological insulator state. These predictions are supported by experimental measures, exhibiting a reduction in bulk conduction with increasing Te/Zr ratio. These findings offer clear guidance for defect control and sample optimization, enabling the robust and reproducible realization of topological quantum states in ZrTe5 for future quantum applications.
Rare-earth high-entropy oxides (RE-HEOs) represent a distinct class of entropy-stabilized ceramics in which multiple lanthanide cations occupy a common crystallographic sublattice, generating strong chemical disorder, lattice distortion, and complex defect landscapes. Unlike transition-metal-based high-entropy oxides, RE-HEOs are governed by localized 4f electronic states, weak crystal-field coupling, and variable redox chemistry, leading to emergent structural, electronic, magnetic, and optical phenomena that challenge conventional solid-state descriptions. This review provides a physics-oriented analysis of RE-HEOs, focusing on the thermodynamic foundations of configurational entropy stabilization, the interplay between enthalpy, entropy, and kinetic trapping, and the consequences of severe chemical disorder for crystal structure and phase stability. We review how lattice distortion, oxygen vacancy disorder, and cation randomness modify phonon spectra, ionic transport pathways, and electronic structures, with particular emphasis on the role of localized 4f states, defect-induced in-gap levels, and disorder-broadened excitation spectra. Spectroscopic manifestations of disorder including crystal-field relaxation, line broadening, lifetime modification, and energy transfer processes are discussed within a unified framework linking local symmetry breaking to macroscopic response. We further discuss the optoelectronic properties of RE-HEOs, including photoluminescence from intra-4f transitions, upconversion mechanisms, and disorder-induced modifications of radiative lifetimes and quantum efficiency. The application landscape spans both energy conversion (electrocatalysis, solid oxide fuel cells, thermal barrier coatings) and optoelectronic technologies (phosphors, scintillators, optical thermometry, and anti-counterfeiting). Likewise, we assess theoretical and computational approaches, including density functional theory with strong correlation corrections, statistical thermodynamics, and emerging machine-learning models, highlighting their ability and current limitations in capturing disorder-driven physics in multi-component oxides. Finally, we identify open questions central to condensed-matter physics, including the nature of entropy-stabilized metastability, the limits of band theoretical descriptions in highly disordered 4f systems, and the role of configurational entropy in tuning electron-phonon and defect interactions. By consolidating experimental and theoretical insights, this review establishes RE-HEOs as a platform for exploring disorder-dominated solid-state physics beyond conventional crystalline oxides.
A global full-dimensional description of interactions in a molecular van der Waals cluster, including both inter and intramolecular degrees of freedom, may seem to be the necessary starting point for high-accuracy nuclear dynamics calculations. Such calculations are currently able to make predictions for clusters, molecular collisions, and condensed phases accurate enough to be confronted with experiment. However, the all-dimensional treatment becomes prohibitively expensive for clusters with more than 6 atoms due to the "curse of dimensionality". On the other hand, the rigid-monomer approximation allows applications to much larger clusters. We show on the example of H2-CO that if the rigidity is imposed via averaging over monomer vibrations, the predictions from such a reduced-dimensionality model can be about as accurate as those from the full-dimensional one; in fact, here both models predict spectra equally well. Moreover, we show that an approximate version of such an averaged surface, based on the Taylor expansion, which does not require the development of a full-dimensional surface and is affordable for larger molecules, also works very well. In contrast, models based on frozen geometries of monomers work much worse. Spectral and scattering calculations with the vibrationally averaged reduced-dimensionality models will result in insights into soft condensed matter properties, cold and ultracold molecular collisions, and physics of cold interstellar clouds that are currently not possible.
The physics in flat bands has emerged as an essential field in condensed matter physics where a plethora of phenomena can be unveiled, such as anomalous transport properties, superconductivity dominated by quantum geometry or exotic topological phases. Our goal here is to show that even in magnetic systems, the presence of flat bands can give rise to unexpected features. More precisely, we address the impact of an Aharonov-Bohm (AB) flux on the exchange couplings in magnetic diamond chains. The most remarkable result is the significant amplification of magnetic couplings at short distances induced by the AB flux, leading to a considerable increase in the thermal conductivity of the magnons. We have also shown that the flux-dependent decaying length of the couplings is connected to the quantum metric of the flat bands. Our results could be of interest for the control of magnetic properties in spintronic devices and relevant for the heat transport by magnons at the nanoscale in quantum technologies.
Quantum sensing with individual spin defects has emerged as a versatile platform to probe microscopic properties of condensed matter systems. Here we demonstrate that quantum relaxometry with nitrogen-vacancy (NV) centers in diamond can reveal the anisotropic spin dynamics of altermagnetic insulators together with their characteristic spin polarised bands. We show that the distance and orientation dependent relaxation rate of a nearby quantum impurity encodes signatures of momentum space anisotropy in the spin diffusion response, a hallmark of altermagnetic order. This directional sensitivity is unprecedented in the landscape of quantum materials sensing, and it enables the distinction of altermagnets from conventional antiferromagnets via local, noninvasive measurements. Our results could spark new NV-sensing experiments on spin transport and symmetry breaking in altermagnets, and highlight the role of NV orientation to probe anisotropic phenomena in condensed matter systems.
Detection of the Higgs mode in superconductors using nonlinear terahertz spectroscopy is a key area of interest in condensed matter physics. We investigate the influence of disorder on the nonlinear terahertz response and the Higgs mode in NbN thin films with varying Ioffe-Regel parameters (k_{F}l). In strongly disordered films near the superconductor-insulator transition, we observe an anomalous third-harmonic generation (THG) signal above T_{c}, which is absent in both cleaner superconducting and nonsuperconducting counterparts. The persistence of this normal-state THG signal in a high magnetic field excludes superconducting fluctuations as its origin. Below T_{c}, the THG intensity increases sharply, indicating a dominant contribution from the driven Higgs mode. The THG spectrum of the strongly disordered sample exhibits a broadened, multipeak structure, which we attribute to quantum path interference between distinct channels involving unpaired electrons and Cooper pairs within emergent superconducting islands. Our findings not only demonstrate how disorder tunes the nonlinear terahertz response, but also uncover a strong coupling between electrons responsible for normal-state THG and the superconducting Higgs mode below T_{c} in strongly disordered samples.
Quantum transport remains a central yet experimentally challenging problem in condensed matter and quantum physics. Here we report the first complete experimental characterization of the full spectrum of quantum transport behaviors in a one-dimensional Fibonacci chain-the paradigmatic quasicrystalline model-spanning localization, subdiffusion, normal and superdiffusion, and ballistic transport. Using a tunable photonic quantum-walk platform, these regimes are unambiguously resolved through their distinct power-law scalings of the mean square displacement and smooth autocorrelation function, together with pronounced oscillatory dynamical structures. These signatures arise from the intrinsic multifractal spectra and hyperuniform order of the Fibonacci quasicrystal, long predicted but never before experimentally resolved. Beyond mapping a comprehensive transport regime diagram, our highly controllable platform provides a powerful and versatile framework for exploring quasiperiodicity, multifractal criticality, and emergent quantum transport phenomena.
Photon condensation in semiconductor microcavities is a transformative technique for engineering quantum states of light at room temperature by tailoring strong but incoherent light-matter inter- actions. While continuous-wave and electrical pumping offer exceptional prospects for miniaturized quantum photonic technologies,harnessing these requires conceptual advances in understanding non- equilibrium light-matter dynamics in semiconductors. We resolve this challenge through an ab initio quantum kinetic theory capturing how Coulomb interactions of optically excited carriers and phonon scattering mediate photon thermalization and condensation in semiconductors. Our microscopic model shows that at high carrier densities, thermalization is dominated by carrier-carrier Coulomb scattering, in clear contrast to the rovibrational relaxation that governs dye-based photon conden- sates. The theory predicts a rich nonequilibrium phase diagram with thermal, Bose-condensed, multimode, and lasing phases, quantitatively in agreement with recent experiments. Crucially, we identify how cavity detuning controls transitions between equilibrium and gain-dominated regimes, enabling tailored design of coherent light sources. This work thus provides the foundation for semiconductor-based quantum photonic devices operating beyond conventional laser paradigms.
Predicting the rate of crystal nucleation is among the most substantial long-standing challenges in condensed matter. In the system most studied (hard-sphere colloids), the discrepancy between experiments and computer simulations is more than 10 orders of magnitude. The situation with other materials (such as water) is no better. Here, we address this challenge with two developments. First, our work is a marked improvement in the precision of mapping the state point of experiments to simulation. For this, we used a combination of novel machine-learning methods for particle tracking and higher-order correlation functions. Second, we consider the free energy of precritical nuclei using confocal microscopy. These are in agreement with computer simulation. This is the first time that such free energies have been successfully compared between experiment and simulation in any material as far as we are aware.
The kinetic theory of soliton gases (SG) is used to develop a solvable model for wave-mean field interaction in integrable turbulence. The waves are stochastic soliton ensembles that scatter off a critically dense SG or soliton condensate-the mean field. The derived two-fluid kinetic-hydrodynamic equations admit exact solutions predicting an induced mean field and SG filtering. The obtained SG statistical moments agree with ensemble averages of numerical simulations. The developed theory readily generalizes, with applications in fluids, nonlinear optics, and condensed matter.
Anomalous Hall effect (AHE), occurring in materials with broken time-reversal symmetry, epitomizes the interplay between magnetic order and electron orbital motions1-4. In two-dimensional (2D) systems, AHE is coupled with out-of-plane orbital magnetization associated with in-plane chiral orbital motions. In three-dimensional (3D) systems, in which sample thickness far exceeds a vertical coherence-transport length lz, the AHE is effectively a thickness-averaged 2D counterpart4-still governed by out-of-plane orbital magnetization arising from in-plane orbital motions. Here we report the experimental observation of a fundamentally new type of AHE that couples both in-plane and out-of-plane orbital magnetizations in multilayer rhombohedral graphene, shown by pronounced Hall resistance hysteresis under both in-plane and out-of-plane magnetic fields. This state emerges from a peculiar metallic phase that spontaneously breaks time-reversal, mirror and rotational symmetries driven by electron-electron interactions. By measuring multiple devices spanning 3-15 layers, we find that this phenomenon emerges only within an intermediate thickness of 2-5 nm. Theoretical calculations show that carriers within this window can sustain coherent orbital motions both within and across the 2D plane. Together, these identify an uncharted 'transdimensional' regime between 2D and 3D, in which the sample thickness is much larger than atomic spacing yet remains comparable to lz, for the emergence of this new state of matter-transdimensional AHE. Our findings point to a distinct class of AHE, opening an unexplored model for correlated and topological physics in transdimensional landscapes.
Ionic conductivity in solids is a topic of great interest in the fields of physics, materials science, and energy applications. Previous studies have primarily focused on the activation energy of ion transport based on classical transition state theory, lacking considerations from the perspective of nuclear quantum effects. Herein, by considering the effects of zero-point energy and quantum tunneling, we examine the quantum behaviors of hydrogen migration in lanthanum trihydrides (LaH3), through the two dominant pathways-concerted migration and single-ion migration. Our first-principles calculations based on instanton rate theory indicate that the quantum rate constants diverge significantly from their classical counterparts at low temperatures. We predict that quantum tunneling becomes dominant over thermal diffusion for concerted hydrogen migration at liquid nitrogen temperature, and emerges even at room temperature when concerted transport is suppressed. We also demonstrate the tuning of migration rates by strain, and the sensitivity of the quantum tunneling rate to the energy barrier geometry. Our findings depict a complete quantum picture of hydrogen transport in lanthanide hydrides and provide a new perspective on ionic conductivity of solid materials.
We investigated the interaction between the monocationic aromatic drug propranolol (PPL) and double-stranded DNA (dsDNA) to elucidate how small molecules can drive higher-order DNA frameworks and nanoparticles (NPs) formation. Single-molecule force spectroscopy with optical tweezers revealed that, at concentrations below 4 mM, PPL interacts with dsDNA through an intercalation-like mode, altering contour length, persistence length, and stretch modulus. At higher concentrations, PPL induced dsDNA compaction, corroborated by atomic force microscopy imaging of condensed structures. Multimolecular assays supported these findings: electrophoretic mobility shift assays revealed progressive mobility loss with increasing PPL concentrations, consistent with aggregate formation, while UV-vis spectroscopy confirmed intercalation-like behavior and strong binding affinity (Kb=1.67 × 10⁶ M⁻¹). At millimolar PPL/DNA ratios (10-14), NPs formulations were obtained with hydrodynamic diameters of 120-244 nm, low polydispersity (0.19-0.30), negative zeta potential (-25 to -35 mV), and particle concentrations up to 5.26 × 10¹¹ NPs/mL. These NPs exhibited very high drug loading (59-72%) and stability under both biological and storage conditions. Collectively, our results demonstrate that PPL engages dsDNA through intercalation-like behavior, compaction, aggregation, and stabilization processes, uncovering a previously unreported mechanism for a monocationic aromatic drug and allowing the efficient formation of NPs. This work expands the current understanding of small molecule-DNA interactions and may be extended to other hydrophilic aromatic drugs, positioning DNA as a versatile building block and ultimately for the development of nucleic acid-based nanomedicines.
We designed antiferromagnetic spin-1/2 chains in fullerene nanoribbons by introducing extra C60 cages at one of their edges. The resulting odd number of intermolecular bonds induces an unpaired π-electron and hence a quantized magnetic moment in otherwise nonmagnetic nanoribbons. We further reveal the formation of an antiferromagnetic ground state upon the linear arrangement of spin-1/2 C60 cages that is insensitive to the specific structural motifs. Janus fullerene nanoribbons may offer an experimentally accessible route to magnetic edge states in low-dimensional carbon nanostructures, possibly serving as a versatile nanoarchitecture for scalable spin-based devices and the exploration of many-body quantum phases.
The magnetic properties of materials similar to Nd-Fe-B permanent magnets are highly sensitive to microstructure. Using Hybrid Monte Carlo micromagnetics simulations, we systematically investigate how grain boundary (GB) and grain crystallographic orientation affect coercivity (Hc) and remanence (Mr). A polycrystalline model with independently adjustable microstructural parameters is constructed via Voronoi tessellation. Our results show that increasing GB width from 2 nm to 10 nm reduces Hc by 32% and Mr by 16%. Grain boundary acts as both a nucleation site and pinning center: a wider GB facilitates reverse domain nucleation, especially at the triple junctions. However, domain wall propagation is underpinned by GB during the propagation process. For a thick GB, Hc decreases with increasing GB saturation magnetization (Ms'), because the thick weakly magnetic layer weakens exchange coupling between adjacent grains, shifting the reversal behavior from collective switching to more localized nucleation. Increasing the average easy-axis tilt angle reduces Hc, as the misalignment lowers the effective anisotropy component along the applied field direction, facilitating magnetization reversal. These findings confirm the importance of GB and texture control in optimizing the magnetic performance of Nd-Fe-B permanent magnets, offering references for experimental investigations.
Water-soluble functionalized fullerenes commonly referred to as fullerenols, fullerols or polyhydroxy fullerenes are widely used in photonics, catalysis, and biomedicine, yet their molecular structures have been assumed to consist solely of hydroxyl groups for nearly three decades. This assumption remains despite persistent mismatches between calculated and experimental vibrational and optical spectra as well as expected and observed chemical reactivity. Here we combine Fourier transform infrared (FTIR) and absorption (UV-Vis) spectroscopy, X-ray photoelectron spectroscopy (XPS), targeted chemical derivatization, and computational quantum chemistry to resolve this discrepancy. We show that only a polyoxy-fullerene architecture incorporating counterion-coordinated carbonyl and hemiketal groups alongside hydroxyls reproduces both the characteristic FTIR features and the experimental UV-Vis absorption profile. A purely hydroxylated fullerene model fails to capture the dominant FTIR band and asymmetric ultraviolet absorption. Oxime-formation experiments chemically validate the presence of carbonyl and hemiketal groups. This structural reassignment resolves long-standing inconsistencies in fullerene chemistry, corrects a pervasive misinterpretation in the literature, and establishes a framework for rationally tuning the optical and chemical properties of functionalized nanocarbons.
Hardware-level security is crucial for establishing trust in the rapidly expanding Internet-of-Things (IoT) and edge computing systems. A promising approach employs physical unclonable functions (PUFs) which leverage intrinsic process variations to generate unique and irreproducible identifiers. However, conventional silicon-based PUFs often suffer from limited entropy and lack of reconfigurability, becoming vulnerable to machine learning attacks. Here, we present an optically reconfigurable PUF based on a 64-cell array of five-stage ring oscillators fabricated from wafer-scale monolayer MoS2. The system exhibits spectrally selective frequency shifts under red, green, and blue (RGB) illumination, establishing a dynamic optical entropy dimension that enables on-demand, reversible rekeying without hardware modification. We develop a robust key-generation pipeline combining within-chip normalization, random-projection q-ary quantization, and the Secure Hash Algorithm 256 (SHA-256) privacy amplification, followed by hash-based message authentication code (HMAC)-based key derivation. The resulting keys demonstrate near-ideal uniformity (~50%) and inter-device Hamming distance (~0.677 at q = 3, 39 ~ 0.761 at q = 4), while remaining resilient to advanced machine learning attacks (≤ 52% accuracy). We further demonstrate image encryption and authentication with noise-like ciphertexts and reliable tamper detection. This work introduces a promising class of material-intrinsic, optically addressable security primitives for trusted edge computing applications.
The pursuit of high-energy-density lithium-ion batteries (LIBs) through high-capacity cathodes (e.g., Ni-rich oxides, lithium-rich manganese oxides) is inevitably accompanied by lattice oxygen release and gas evolution, yet the systemic impacts of oxygen crossover in full-cell configurations remain underexplored. This study investigates how oxygen gas permeation across separators triggers capacity degradation in LIBs. By regulating separator permeability and employing differential electrochemical mass spectrometry (DEMS), we quantify oxygen transport pathways and their correlation with interfacial instability. Combined with cryogenic transmission electron microscopy and atomic force microscopy, we reveal that cathode-derived oxygen penetrates separators, attacking the anode to exacerbate heterogeneous solid electrolyte interphase (SEI) growth and mechanical destabilization. Continuous SEI fracture-reconstruction during cycling accelerates active lithium depletion and capacity fading. Employing low-permeability separators can effectively mitigate oxygen crossover and double the cycle life through stabilization of the anode interface. These findings establish oxygen gas crossover as one of the critical yet overlooked degradation vectors, bridging the knowledge gap between cathode oxygen release and anode failure mechanisms.
Excitons play a crucial role in optical properties of two-dimensional materials. While significant progress has been made in understanding exciton dynamics on femtosecond timescales, the microscopic details of the earliest stages of exciton formation and evolution remain elusive. Here we explore the ultrafast processes of exciton formation, evolution and dissociation in monolayer hexagonal boron nitride using state-of-the-art time-dependent density functional theory simulations incorporating long-ranged interactions. We find that the exciton forms within ~2.5 fs through a three-step process: free carriers are first generated by photoexcitation; electrons and holes subsequently bind to form a metastable "exciton core"; and finally, the exciton core evolves into a fully-formed exciton. The subsequent dynamics are dominated by exciton-exciton interference, which gives rise to oscillatory electron-occupation signals. These signals serve as a predicted phase-sensitive signature, providing a theoretical basis for experimentally probing the exciton envelope phase. This interference can be further modulated and an anisotropic Mott transition is induced upon increasing laser intensity into the strong field regime.
Azobenzene derivatives, especially seven-membered cyclic compounds such as dibenzo[b,f][1,4,5]thiadiazepine (DBTD), are considered promising candidates for molecular solar thermal (MOST) energy storage systems due to their significant energy storage capabilities. In contrast, its structural analogue, dibenzo[b,f][1,4,5]oxadiazepine (DBOD), fails to exhibit substantial Z → E photoisomerization, despite possessing a higher isomerization energy. In this study, we investigated the underlying mechanistic causes of this paradox by comparing the photoisomerization dynamics of DBTD and DBOD through electronic structure calculations and nonadiabatic molecular dynamics (NAMD) simulations. Our results revealed that, while photoexcitation leads to the formation of the E-isomer in DBOD, its metastable E-configuration rapidly relaxes back to the Z-form within 400 fs at room temperature. This rapid back-conversion arises from three synergistic factors: (i) a lower thermal isomerization barrier, (ii) substantial kinetic energy retained upon de-excitation, and (iii) preferential allocation of kinetic energy into azo-group torsional modes, which together accelerate the reverse reaction on the ground state. To mitigate this issue, we proposed a synergistic strategy combining fluorine substitution with low-temperature regulation. Fluorination yields perfluorodibenzo[b,f][1,4,5]oxadiazepine (PDOD), which increases the thermal E → Z isomerization barrier while preserving a high isomerization energy of 164.3 kJ/mol. NAMD simulations at 100 K show that the E-isomer of PDOD remained stable for over 400 fs, with a Z → E quantum yield of 26%, significantly higher than the 19% quantum yield of DBOD at 300 K. This study provides mechanistic insights into the "high isomerization energy yet poor stability" paradox observed in DBOD and establishes a practical strategy for developing high-performance MOST photoswitches.