Beyond the Kubo formula: unification of adiabatic and isothermal response in quantum systems
Abstract
The static limit of the Kubo susceptibility describes the adiabatic response of an isolated quantum system, in which energy-level occupations remain unchanged, and generally differs from the isothermal susceptibility, where these occupations readjust to thermal equilibrium. In this work, we introduce a single dynamical framework in which the adiabatic and isothermal responses arise naturally as two distinct limiting regimes. This can be done by considering explicitly an open system version of the Kubo approach in which the dissipation is governed by a typical thermalization rate of the system. By exchanging the order of the static limit and of the vanishing thermalization rate limit, the protocol yields either the adiabatic or isothermal response. This protocol has a solid physical motivation in terms of the thermalization dynamics and is valid for generic systems. We apply it to the case of the magnetic response of the electron gas and reproduce the expected results.
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BibTeX
@misc{chiriaco2026beyond,
title = {{Beyond the Kubo formula: unification of adiabatic and isothermal response in quantum systems}},
author = {Giuliano Chiriacò and Vasco Cavina},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.40810},
eprint = {2610.40810},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.40810},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Beyond the Kubo formula: unification of adiabatic and isothermal response in quantum systems
AU - Giuliano Chiriacò
AU - Vasco Cavina
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2610.40810
UR - https://arxiv.org/abs/2610.40810
AB - The static limit of the Kubo susceptibility describes the adiabatic response of an isolated quantum system, in which energy-level occupations remain unchanged, and generally differs from the isothermal susceptibility, where these occupations readjust to thermal equilibrium. In this work, we introduce a single dynamical framework in which the adiabatic and isothermal responses arise naturally as two distinct limiting regimes. This can be done by considering explicitly an open system version of the Kubo approach in which the dissipation is governed by a typical thermalization rate of the system. By exchanging the order of the static limit and of the vanishing thermalization rate limit, the protocol yields either the adiabatic or isothermal response. This protocol has a solid physical motivation in terms of the thermalization dynamics and is valid for generic systems. We apply it to the case of the magnetic response of the electron gas and reproduce the expected results.
ER -