David Huse – Princeton University
Date/Time/Location
Thursday, April 9, 2026, 12:10 pm; Hill Center 705
Thermal first-order phase transitions and the eigenstate thermalization hypothesis
A many-body system with a thermal first-order phase transition exhibits an extensive discontinuity in the energy and entropy (the latent heat) at the phase transition, within the canonical ensemble. There are states within the energy range that is “skipped over” by this canonical ensemble first-order phase transition, and these states may be studied in the microcanonical ensemble and in particular in the limit of the microcanonical “ensemble” for a closed quantum many-body system that is a single energy eigenstate. To make this a tractable semi-classical calculation we study a class of infinite-range models exhibiting this physics. Such models can have a microcanonical first-order phase transition (that occurs “within” the canonical first-order transition) where the energy and entropy are both continuous, but the temperature is a discontinuous function of the energy. At this microcanonical transition, the eigenstates of an otherwise quantum-chaotic system may either be “localized” within one of the two coexisting phases, or they may contain Schrodinger-cat-like phase coexistence within a single eigenstate.
Ref: Serbyn, Avdoshkin, Diessel and Huse, arXiv:2601.08347 .