RQC Seminar

54th RQC Seminar

• Speaker

  Dr. Fredrik Brange
  ( Department of Applied Physics, Aalto University, Finland )

• Date

  15:00-16:00, June 23, 2023 (Friday)

• Venue

  Hybrid(ZOOM・ Wako Main Research 3F 345-347 Seminar Room （C01））

• Title

  Lee-Yang theory of non-equilibrium phase transitions in quantum many-body systems

• Inquiries

  rqc_info[at]ml.riken.jp

Abstract
Phase transitions are ubiquitous phenomena in physics, characterized by the sudden change of a physical quantity in response to variations in an external control parameter. In this talk, I will introduce Lee-Yang theory as a tool for predicting and investigating phase transitions. Lee-Yang theory utilizes the zeros of a (generalized) partition function in the complex plane of the control parameter. While these zeros are non-real for finite-size systems, they may approach a point on the real axis in the thermodynamic limit, signifying the occurrence of a phase transition. I will demonstrate how the exploration of Lee-Yang zeros provides insights into equilibrium and non-equilibrium phase transitions in various quantum many-body systems, such as Bose-Einstein condensation in a gas of bosons, abrupt changes in the activity of a single-electron micromaser, and dynamical quantum phase transitions in quenched spin lattices. Moreover, I will discuss experimental approaches to determine the zeros through measurements of fluctuations in the conjugate variable of the control parameter.