SKM 2023 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 30: Nonequilibrium Quantum Many-Body Systems II (joint session TT/DY)

DY 30.8: Talk

Wednesday, March 29, 2023, 17:00–17:15, HSZ 204

Maximally chaotic to Fermi liquid crossover in a generalized SYK model — •Nick von Selzam and Stefan Kehrein — Institute for Theoretical Physics, University of Göttingen, Germany

We consider a generalized Sachdev-Ye-Kitaev (SYK) model: Majorana fermions on N sites with random q/2-body all to all interactions plus a kinetic energy term.

The SYK model can be seen as a toy model for quantum chaos and does not allow for a quasiparticle description. We discuss the continuous crossover between the Fermi liquid regime, dominated by the kinetic term, and the maximally chaotic regime, dominated by the SYK interaction, by studying the quantum Lyapunov exponents.

For fixed interaction strength there exists a crossover temperature for which the Lyapunov exponent becomes maximal. For lower temperatures the Lyapunov exponent is exponentially small. For larger temperatures the behaviour is close to indistinguishable from the pure SYK term.