MajuLab Seminar by Xiansong Xu – 8 February 2023

MajuLab Seminar: Wednesday 8 February 2023 | CQT Level 5 Seminar room  4:30 PM Singapore time | 9:30 AM French time
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Xiansong Xu, Singapore University of Technology and Design
Xiansong Xu

Xiansong Xu 

Xiansong Xu is a postdoctoral research fellow at Singapore University of Technology and Design. His main research interests are techniques in open quantum systems such as quantum master equations and tensor network methods. He is also interested in the foundational aspects of nonequilibrium statistical mechanics such as thermalization and typicality.  


We study the steady currents between two finite nonintegrable environments. Each environment is able to thermalize by itself following the so-called eigenstate thermalization hypothesis. With typical initial states for each bath, i.e., random superposition of eigenstates within certain energy shell, we first that the emergent steady currents are also typical, i.e., the vast majority of the current has a value close to steady current obtained from baths with microcanonical initial conditions. We then show that the formation of the steady currents is a manifestation of the prethermalization phenomenon, a quasi equilibrium dynamical process with weak breaking of conserved quantities. We then study more generalized initial states, i.e., a random product state with fixed and different energy constraints (within the mean energy ensemble). Such an initialization, not being constrained to superpositions or mixtures of many-body eigenstates, opens the door to experimental realization and also significantly simplifies numerical simulations. We again show that such dynamical process is typical as the current variance decreases exponentially with respect to the size of baths. Particularly, we demonstrate that the emerging current is prethermalized in a strong sense, analogously to strong thermalization, meaning that the current values stay close to the microcanonical one most of the time.


MajuLab is an international joint research unit of the CNRS, UCA, SU, NUS and NTU in Singapore (IRL 3654), hosted by CQT and SPMS.