Dresden 2026 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 30: Nonequilibrium Quantum Systems I (joint session TT/DY)

DY 30.12: Talk

Wednesday, March 11, 2026, 12:30–12:45, CHE/0091

Emergent Fermi surfaces from non-equilibrium heat baths: exact results from Keldysh formalism — •Akihiro Ozawa and Inti Sodemann Villadiego — Institut für Theoretische Physik, Universität Leipzig, 04103, Leipzig, Germany

Recent studies have shown that periodically driven fermions coupled to a boson bath display non-analyticities in their occupation functions of momentum that behave like emergent Fermi surfaces. Remarkably, we have found that analogous non-equilibrium emergent Fermi surfaces can arise when the system is coupled to two baths at different temperatures, even without external periodic driving. The mechanism driving the formation of these non-equilibrium Fermi surfaces, is a kind of transfer from non-analyticities from the density of states into the occupation of states which is only allowed away from equilibrium, in the absence of detailed balance in the scattering rates. We demonstrate that this result is exact at weak coupling using the Keldysh formalism and propose a numerical scheme to investigate the fate of these non-analyticities at finite coupling.

Keywords: Emergent Fermi surface; Heat bath; Keldysh formalism