Universal behaviour when cooling down to quantum criticality
Date: 12 JULY 2023 from 11:00 to 12:00
Event location: Sala IR-1A
Signatures of equilibrium phase transitions can be imprinted into the
nonequilibrium dynamics of many-body quantum systems, resulting in the
emergence of universal scaling laws out of equilibrium, as exemplified by the
Kibble-Zurek mechanism. In a similar spirit, but novel setting, I report
scaling and universality in open nonequilibrium quantum systems that are cooled
towards a quantum critical point. The excess excitation density, which
quantifies the degree of adiabaticity of the dynamics, is found to obey scaling
laws in the cooling velocity as well as in the initial and final temperatures
of the cooling protocol. The scaling laws are universal, governed by the
critical exponents of the quantum phase transition. The validity of these
statements is shown analytically for a Kitaev quantum wire coupled to Markovian
baths, and subsequently argued to be valid under rather general conditions.
Remarkably, these results establish that quantum critical properties can be
probed dynamically at finite temperature, without even varying the control
parameter of the quantum phase transitions.