Max Planck Institute for the Physics of Complex Systems

地点：M830

摘要：

In the first part, I will introduce the quantum geometry in superconductors. In flat-band systems, the Fermi velocity vanishes and the effective mass diverges, leading to the failure of conventional BCS relations, such as the coherence length ξ=ℏv_f/Δ and the superfluid weight D_s = 1/m^*. I will discuss the establishment of Ginzburg-Landau (GL) theory concerning the coherence length of flat-band superconductors. From this theory, we find that the superconducting coherence length is not determined by Fermi velocity but rather by the size of optimally localized Wannier functions, which is constrained by the quantum metric. In the second part, I will talk about the delocalization effect from the disorders in the one-dimensional metal-flat band-metal junction. We reveal that disorders can induce delocalization and enable the control of transmission through quantum geometry. In the weak disorder regime, transmission is primarily mediated by interface-bound states, whose localization length is determined by the quantum geometry of the system. As disorder strength increases, a zero-energy transmission channel - absent in the clean system - emerges, reaches a maximum, and then diminishes inversely with disorder strength in the strong disorder limit. In the strong disorder regime, the transmission increases with the localization length and eventually saturates when the localization length becomes comparable to the link size.

报告人简介：

Shuai Chen is currently a postdoctoral researcher at the Max Planck Institute for the Physics of Complex Systems. He graduated from Tianjin University in 2016 and completed his PhD in Institute for Advanced Study at Tsinghua University in 2021. From Sept 2021 to Oct 2023, he held a postdoctoral fellowship at the Hong Kong University of Science and Technology (HKUST), where he later became a Research Assistant Professor until June 2024. His research interests include strongly correlated systems and high-temperature superconductors, with a current focus on quantum geometry and interactions in flat-band systems.

邀请人：李自翔

Email: zixiangli@iphy.ac.cn