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TT: Fachverband Tiefe Temperaturen

TT 86: Correlated Electrons: Method Development

TT 86.11: Talk

Friday, March 22, 2024, 12:15–12:30, H 3007

Thermodynamic stability at the two-particle level — •Alexander Kowalski¹, Matthias Reitner², Lorenzo Del Re^3,4, Maria Chatzieleftheriou^5,6, Adriano Amaricci⁷, Alessandro Toschi², Luca de' Medici⁵, Giorgio Sangiovanni¹, and Thomas Schäfer⁴ — ¹Institut für Theoretische Physik und Astrophysik und Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg — ²Institute for Solid State Physics, TU Wien — ³Department of Physics, Georgetown University — ⁴Max-Planck-Institut für Festkörperforschung — ⁵Laboratoire de Physique et d'Étude des Matériaux, UMR8213 ESPCI — ⁶CPHT, CNRS, École polytechnique — ⁷CNR-IOM, Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche

We show how the stability conditions for a system of interacting fermions that conventionally involve variations of thermodynamic potentials can be rewritten in terms of local one- and two-particle correlators. We illustrate the applicability of this alternative formulation in a multi-orbital model of strongly correlated electrons at finite temperatures, inspecting the lowest eigenvalues of the generalized local charge susceptibility in proximity of the phase-separation region. Additionally to the conventional unstable branches, we analyze unstable solutions possessing a positive, rather than negative compressibility. Our stability conditions require no derivative of free energy functions with conceptual and practical advantages for actual calculations and offer a clear-cut criterion for analyzing the thermodynamics of correlated complex systems.

Keywords: thermodynamic stability; phase transition; two-particle correlation function