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arXiv · 2604.21283

Electrically switchable vacancy state revealed by in-operando positron experiments

Ric Fulop·Laurence Lyons IV·Robert Nick·Marc H. Weber·Ming Liu·Haig Atikian·Uwe Bauer·Alexander C. Barbati·Neil Gershenfeld
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Abstract

Whether the flash state in electrically driven solids involves non-equilibrium defect production or is accounted for by Joule heating alone has been debated since 2010. Using positron annihilation spectroscopy on copper, we observe a fully reversible, electrically switchable vacancy population: the DBS S-parameter rises above baseline whenever applied current exceeds a critical density and returns on current removal. Positron lifetime spectroscopy independently confirms open-volume defect formation and reveals a void to cluster relaxation hierarchy. The current-induced vacancy concentration exceeds the thermal-equilibrium value at 352C by > 106x, is present only while current is applied, and vanishes within minutes. The nucleation rate scales steeply with the applied current, connecting the minute-scale kinetics resolved here to the sub-second flash events observed in ceramic sintering. These results demonstrate current-induced Frenkel-pair production in a metal and identify a defect-mediated, non-equilibrium contribution to the flash state.

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Ric Fulop, Laurence Lyons IV, Robert Nick, Marc H. Weber, Ming Liu, Haig Atikian, Uwe Bauer, Alexander C. Barbati, Neil Gershenfeld. 2026-04-23. Electrically switchable vacancy state revealed by in-operando positron experiments. https://arxiv.org/abs/2604.21283

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