报告题目：Microscopic study of vortex state in Fe-based superconductors: from signature of MZM to vortex pinning mechanism

报  告  人：张童，复旦大学

报告时间：2025年3月6日16：00

报告地点：物理楼（附中南侧）W101

内容摘要：In type-II superconductors, external magnetic field induces the formation of quantized flux/vortex. These vortices carry information of superconducting pairing and can host exotic quasiparticles, such as Caroli-de Gennes-Matricon (CdGM) states and Majorana zero modes (MZMs). Additionally, the response of vortices to external electrical current, such as vortex pinning effect, profoundly influences the transport properties of practical superconductors. In this talk, I will present our microscopic studies of vortex state in iron-based superconductors, including (Li,Fe)OHFeSe and 1ML FeSe/STO. Utilizing high-energy resolution scanning tunneling spectroscopy, we observed zero-energy modes, CdGM states and determined their spatial distributions. The zero-mode show characteristics of MZM. Furthermore, we explored vortex pinning effects at atomic-scale. We found that defect-vortex interactions shift low-energy CdGM states away from Fermi energy, thereby reducing the vortex energy and explained why the vortices are pinned by point defects. Based on these findings, we propose a general mechanism of vortex pinning in superconductors.

报告人简介：张童，2004 年本科毕业于山东大学物理系， 2010 年于中国科学院物理研究所获得博士学位， 2010-2012 年在美国 NIST 做博士后研究，现任复旦大学物理系教授。主要利用极低温扫描隧道显微镜 (STM) 、高分辨隧道谱、外延薄膜生长等研究非常规超导体和拓扑材料。在包括 Nat. Phys. ， PRL ， PRX ， Sci. Adv. ， Nat. Communi. 在内的期刊上发表论文 60 余篇，被引 6 千余次。