Regensburg 2025 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 22: Many-body Systems: Equilibration, Chaos, and Localization (joint session DY/TT)

TT 22.5: Vortrag

Dienstag, 18. März 2025, 15:00–15:15, H37

Impurity coupled to the SYK bath — •Anastasia Enckell and Stefan Kehrein — Institute for Theoretical Physics, Georg-August-Universität Göttingen, Germany

System-plus-bath models play an important role in addressing fundamental questions in condensed matter physics. One challenging aspect is modelling the bath, which is often approached using free-particle or open quantum system frameworks. Here, we explore the Sachdev-Ye-Kitaev (SYK) model as a new kind of quantum bath with unique properties, including the absence of quasiparticles, maximal chaos, and non-integrability, which make it a valuable framework for studying system-plus-bath interactions. We study the time evolution of the occupation of an impurity coupled to the SYK bath following a quench. From the Kadanoff-Baym equations for a noninteracting impurity, we see that the only relevant property for the impurity occupation is a combination of hybridisation and density of states of the bath. These parameters can be adjusted in order to model the impurity coupled to any bath of interest. Using this approach, we can study the impurity dynamics coupled to the SYK bath by making suitable changes to the hybridisation in impurity plus Fermi bath setting, which significantly simplifies the task. We observe oscillatory dynamics of the impurity at zero temperature, with the oscillations decreasing as the temperature increases. This behaviour contrasts with that of a free-particle bath and suggests interesting underlying physics.

Keywords: SYK bath; Fermi bath; impurity; Sachdev-Ye-Kitaev model; system-plus-bath