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

Erik S. Lamb; Nicolò D'Anna; Phillip Ridley; Nelson Hua; Ivan Zaluzhnyy; James Burrow; Emilio Escauriza; Robin Glefke; Boyan K. Stoychev; Mingze Wan; Zhe Ren; Fabian Westermeier; Michael Sprung; Alex Frañó; Ying Shirley Meng; Oleg G. Shpyrko

arXiv · 2611.04547

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

Erik S. Lamb·Nicolò D'Anna·Phillip Ridley·Nelson Hua·Ivan Zaluzhnyy·James Burrow·Emilio Escauriza·Robin Glefke·Boyan K. Stoychev·Mingze Wan·Zhe Ren·Fabian Westermeier·Michael Sprung·Alex Frañó·Ying Shirley Meng·Oleg G. Shpyrko

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Abstract

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.

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Erik S. Lamb, Nicolò D'Anna, Phillip Ridley, Nelson Hua, Ivan Zaluzhnyy, James Burrow, Emilio Escauriza, Robin Glefke, Boyan K. Stoychev, Mingze Wan, Zhe Ren, Fabian Westermeier, Michael Sprung, Alex Frañó, Ying Shirley Meng, Oleg G. Shpyrko. 2026-11-03. Strain-Glass Dynamics in the Superionic Conductor Na$_3$PS$_4$. https://arxiv.org/abs/2611.04547

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