题目：Quantum metric lengths in superconducting anddisordered systems

报告人：Kam Tuen Law(罗锦团)

时间：2026年5月12日(周二)下午15:30

地点：紫金港校区段永平教学楼2号楼212报告厅

摘要：

In most solid state systems, the Fermi velocity combined with energy gives rise to manyimportant length scales such as the coherence length and the superconducting coherencelength. As Fermi velocity goes to (nearly) zero in flat band materials, these conventional lengthscales vanish. The question is: in flat band materials, what gives rise to the important lengthscales?

In this talk, we show that the quantum metric length, which was known to determine the size ofthe optimally localized Wannier functions, is indeed the fundamentally important length scale inflat band materials, We show that, while the auantum metric enath can be exceedinaly ong. itdetermines the superconducting coherence length of flat band superconductors [1,2], thecoherence length of a flat band josephson junction [3], the decay length of Majorana modes inflat band topological superconductors [4]and more. The critical current anomaly had beenobserved experimentally in flat band josephson junction can be explained by quantum metriccontributions [5].

Recently, we showed that the guantum metric length determines the localization lenath ofdisorder flat band materials, Take a 1D svstem with a flat band (with a small dispersion ) as anexample. As disorder increases, the localization length decreases as expected from Andersonlocalization. However, as disorder further increases, the localization length reaches a plateauwhere the localization length is about twice the quantum metric length. The plateau isextremely wide for an isolated flat band, We call this regime where the localization lenath isgoverned by the quantum metric length, the quantum metric localization regime [6].

1.Shuai A. Chen and K.T. Law, Phys.Rev.Lett.132.026002(2024).

2.JX Hu, SA Chen.KT Law,Communications Physics 8.20.(2025).

3. Zhong CF Li, Yuxuan Deng, Shuai A Chen, Dmitri K Efetov, KT Law, Phys. Rev. Research 7.023273 (2025).

4. Xingyao Guo, Xinglei Ma, Xuzhe Ying, KT Law Phys. Rev. Lett. 135.076601 (2025).

5. A Diez-Carlon, J Diez-Merida, P Rout, D Sedov, P Vitanen, S Baneriee, RPS Penttila, P Altpeter, K Watanabe, T Taniguchi, S-yYang, KT Law, TT Heikkila, P Torma, MS Scheurer, DK Efetov, Phys. Rev.X 15, 041033 (2025).

6.Chun Wang Chau, Tian Xiang, ShuaiA Chen, KT Law, arXiv:2602.01354.

个人简介：

罗锦团教授现任香港科技大学物理学系讲座教授。2003年毕业于香港科技大学物理系，并于2008年取得布朗大学博士学位。博士毕业后，以裘博士后研究员身份在麻省理工学院师从Patrick Lee教授开展研究。他在拓扑超导体和其他拓扑材料的研究方面做出了开创性的贡献。2015年，他与荷兰和美国的两个实验小组共同发现了一种新型超导体，并将其命名为「伊辛超导体」。罗教授曾获2015年裘槎前瞻科研大奖，2023年获全球华人物理和天文学会颁发亚洲成就奖，2024年获选美国物理学会会士，2025年11月入选新基石研究员。