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Fractional Impurity Entropy from Potential Scattering in a Free Electron Gas
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 kBln√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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BibTeX
@misc{zaidi2026fractional,
title = {{Fractional Impurity Entropy from Potential Scattering in a Free Electron Gas}},
author = {Syeda Neha Zaidi and Jukka I. Väyrynen},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.29007},
eprint = {2608.29007},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.29007},
}
RIS
TY - UNPB
TI - Fractional Impurity Entropy from Potential Scattering in a Free Electron Gas
AU - Syeda Neha Zaidi
AU - Jukka I. Väyrynen
PY - 2026
DA - 2026/08/29
PB - arXiv
DO - 10.48550/arxiv.2608.29007
UR - https://arxiv.org/abs/2608.29007
AB - 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_Bln√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.
ER -