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arXiv · 2608.29007

Fractional Impurity Entropy from Potential Scattering in a Free Electron Gas

Syeda Neha Zaidi·Jukka I. Väyrynen
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Abstract

Fractional changes in entropy are often associated with strong electron correlations or non-Abelian anyons in topological systems. We show that neither condition is necessary -- a system of free electrons on a ring scattering off a repulsive point-like impurity undergoes a $k_B\ln\sqrt 2$ entropy change as the impurity strength is increased. This effect arises from a shift of allowed single-particle momenta from integer quantization to half-integer quantization, induced by the impurity. We show that this fractional entropy change is universal across a broad class of single-particle dispersions, demonstrating that such signatures can arise without strong correlations or topological order.

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Syeda Neha Zaidi, Jukka I. Väyrynen. 2026-08-29. Fractional Impurity Entropy from Potential Scattering in a Free Electron Gas. https://arxiv.org/abs/2608.29007

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