Title: Dissipative Phase Transition in the Quantum Rabi Model with a Structured Environment

Speaker: Mark Mitchison (Trinity College Dublin)

Abstract: I will introduce the super-radiantquantum phase transition in the Rabi model and its dissipative generalisation [1,2]. I will then extend the model to include both a structured bath (i.e. frequency-dependent noise) and pure white noise. The frequency dependence of the noise is found to strongly modify the critical exponents and the dynamics of the system close to criticality. Remarkably, in the sub-Ohmic regime an unconventional second-order phase transition arises, in which the soft-mode frequency and decay rate remain finite across the critical point. This strongly suppresses the critical exponent describing the behaviour of fluctuations close to the transition. I will describe how these unusual effects compete with standard features of second-order quantum criticality induced by white noise and/or finite temperature.

Time: Thursday, 12 September 2019, 2:30pm

Location: Lecture Room, 1st Floor, School of Theoretical Physics, DIAS,
10 Burlington Road, Dublin 4