报告题目：How can a zero-dimensional superradiant phase transition occur?

报告人： 葛自勇 博士后研究员 （日本理化研究所）

报告时间：2024年1月5日（星期五）14：30-16：30

报告地点：北洋园校区 49 教 410 室 （线上：腾讯会议 582-4097-0849）

报告摘要：

The existence of zero-dimensional superradiant quantum phase transitions seems inconsistent with  conventional statistical physics. In this talk, I will clarifiy this apparent inconsistency. I mainly demonstrate the corresponding effective field theories and finite-temperature properties of light-matter interacting systems, and show how this zero-dimensional quantum phase transition occurs. I first focus on the Rabi model, which is a minimum model that hosts a superradiant quantum phase transition. With the path integral method, I derive the imaginary-time action of the photon degrees of freedom. I also define a dynamical critical exponent as the rescaling between the temperature and the photon frequency, and perform dimensional analysis to the effective action. The dynamical critical exponent shows that the effective theory of the Rabi model is a free scalar field, where a true second-order quantum phase transition emerges. These results can also be verified by numerical simulations of imaginary-time correlation functions of the order parameter. I also generalize this method to the Dicke model.

报告人简介：

       葛自勇于2016年获得华中科技大学学士学位，2021年获得中科院物理所博士学位，2021年10月至今就职于日本理化学研究所，为博士后研究员，合作导师为Franco Nori。目前主要从事量子多体物理和量子模拟理论研究，已发表学术论文10余篇。