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DY: Fachverband Dynamik und Statistische Physik

DY 62: Critical Phenomena and Phase Transitions

DY 62.6: Vortrag

Freitag, 20. März 2020, 11:00–11:15, ZEU 118

Fermionic Criticality Out-of-Equilibrium — •Bernhard Frank — Max-Planck-Institut für Physik komplexer Systeme — Dresden

Critical Fermions, like strange metals, exhibit correlation functions with universal, anomalous power laws, which lead to deviations from Fermi liquid results both for thermodynamic and transport quantities. Coupling a massless bosonic degree of freedom to the Fermi surface provides one mechanism to create these unconventional states of matter that so far have only been studied in thermal equilibrium. However, recent experiments combine semi-conductor devices with optical cavities and therefore mandatorily require a theoretical formulation that takes into account the intrinsically driven-dissipative nature of the photon in order to understand the electronic many-body state. Based on Keldysh quantum field theory we study a simple two-dimensional model for a stange metal out-of-equilibrium. Compared to the situation in the ground state one observes increased decay rates in the low-energy sector of the fermionic spectrum as well as a violation of the thermal fluctuation dissipation relation caused by the enhanced bosonic fluctuations generated by the drive.