主讲人：Sergej Flach 教授（韩国基础科学研究院）

题目：Flat Band Physics

时间：2024年07月27日下午15：00

地点：理工楼1201

邀请人：王宜森

报告摘要：

Flat bands – single-particle energy bands – in tight-binding networks have attracted attention due to the presence of macroscopic degeneracies and their extreme sensitivity to perturbations. This makes them natural candidates for emerging exotic phases and unconventional orders. The challenging part however is to construct flat band networks, whose existence relies on symmetries and fine-tuning. In this talk we consider the recently proposed systematic ways to construct flat band networks based on symmetries or finetuning. We then discuss how the fine-tuning constructions can be further extended, adapted or exploited in presence of perturbations, both single-particle and many-body. This strategy has lead to the discovery of non-perturbative metal-insulator transitions, fractal phases, nonlinear and quantum caging and many-body nonergodic quantum models. We discuss what implications these results may have for the design of fine-tuned nanophotonic systems including photonic crystals, nanocavities, and metasurfaces

个人简介：

Prof. Sergej Flach is the Director of the Center for Theoretical Physics of Complex Systems, established in December 2014. He earned both his M.A. and Ph.D. from the Dresden University of Technology in Germany between 1986 and 1989. After an Alexander-von-Humboldt fellowship at TU Munich and postdoctoral work at Boston University, he joined the Max Planck Society in 1994. From 2012 to 2016, he was a professor at the New Zealand Institute for Advanced Study. Prof. Flach's research focuses on nonlinear quantum and classical waves in complex systems, Fano resonances in nanoscale structures, and exciton-polariton Bose-Einstein condensates. He has over 240 publications and has received several awards, including the Stefanos Pnevmatikos Award for Nonlinear Science. He also serves on the editorial boards of major scientific journals and has coordinated numerous workshops and conferences.