Mingze Wan | Searcharxiv

arXiv2026

Strain-Glass Dynamics in the Superionic Conductor Na$_3$PS$_4$

Ionic conduction in solid-state electrolytes is conventionally described by mobile cations migrating through a static host lattice. Yet the fastest conductors are often the most disordered, and how disorder enhances transport remains unresolved at the mesoscale, inaccessible to ensemble-averaged probes. We use Bragg X-ray photon correlation spectroscopy to measure nanoscale structural dynamics of a single ball-milled Na$_3$PS$_4$ particle. We find that the cubic phase behaves as a strain glass: a frustrated configuration of three degenerate tetragonal variants with short-range order. Its domain-wall motion is stress-driven, crossing over irreversibly to thermally activated dynamics on annealing as residual milling stress is depleted. Rearrangements follow scale-free avalanche statistics, matching ferroelastic martensites but without external driving. The tetragonal polymorph shows none of these features and relaxes fifty times more slowly. These dynamics occur on timescales comparable to estimated ionic diffusion across the particle, indicating the host structure cannot be assumed static on transport-relevant timescales.

cond-mat.mtrl-sci↗

arXiv2025

Self-strain suppression of the metal-to-insulator transition in phase-change oxide devices

Quantum materials exhibiting phase transitions which can be controlled through external stimuli, such as electric fields, are promising for future computing technologies beyond conventional semiconductor transistors. Devices that take advantage of structural phase transitions have inherent built-in memory, reminiscent of synapses and neurons, and are thus natural candidates for neuromorphic computing. Of particular interest are phase-change oxides, which allow for control over the metal-to-insulator transition. Here, we report X-ray nano-diffraction structural imaging of micro-devices fabricated with the archetypal phase-change material vanadium sesquioxide (V$_2$O$_3$). The devices contain a Ga ion-irradiated region where the metal-to-insulator transition critical temperature is lowered, a useful feature for controlling neuron-like spiking behavior. Results show that strain, induced by crystal lattice mismatch between the pristine and irradiated material, leads to a suppression of the metal-to-insulator-transition. Suppression occurs within the irradiated region or along its edges, depending on the defect-distribution and the size of the region. The observed self-straining effect could extend to other phase-change oxides and dominate as device dimensions are reduced and become too small to dissipate strain within the irradiated region. The findings are important for phase engineering in phase-change devices and highlight the necessity to study phase transitions at the nanoscale.

cond-mat.mes-hall↗