报告题目：Topological Superfluid Responses of Superconducting Dirac Semimetals

报告人：Panagiotis Kotetes 副研究员（中国科学院理论物理研究所） 

报告时间：2024年4月19日（星期五）15：30-16：30

报告地点：北洋园校区49教410室（线上：腾讯会议 838-9499-4192）

报告摘要：

In this talk, I bring forward that topological constraints do not only dictate the geometric part of the superfluid stiffness, as it has been recently shown, but can also govern the total superfluid stiffness. By introducing a general adiabatic approach for superfluid responses, I demonstrate such a possibility by proving that the stiffness of a superconducting Dirac cone in two dimensions (2D) is proportional to its topological charge. By relying on the emergent Lorentz invariance of Dirac electrons, I further discuss that the superfluid stiffness and the Josephson quantum capacitance can be unified in these systems. Based on this connection, I also predict a topological origin for the quantum capacitance of a Josephson junction where 2D massless Dirac electrons are sandwiched between two conventional spin-singlet superconductors. Moreover, I show that the topological responses persist upon effecting strain, are resilient against weak disorder, and can be experimentally controlled via a Zeeman field. Remarkably, the nonuniversal topological quantization of the two superfluid responses, yet implies the universaltopological quantization of the admittance modulus of the superconducting Dirac system in units of conductance. The here-termed quantum admittance effect arises when embedding the superconducting Dirac system in an ac electrical circuit with a frequency tuned at the absorption edge. These findings can be in principle experimentally observed in graphene-superconductor hybrids.

报告人简介：

Panagiotis Kotetes is since the beginning of 2019 an Associate Professor at the Institute of Theoretical Physics of the Chinese Academy of Sciences in Beijing. During the years 2015-2018 he served as a postdoctoral researcher at the Niels Bohr Institute of the University of Copenhagen. Before that, he had a postdoctoral appointment at the Karlsruhe Institute of Technology, where he worked for five years. Panagiotis carried out his Diploma, Masters and Ph.D. studies at the National Technical University of Athens in Greece. His research interests and activity cover the topics of topological materials and nanodevices, unconventional superconductivity, exotic magnetism, and quantum computing. Up to date, Panagiotis has published more than 40 scientific articles in journals including Physical Review X and Letters, while he has also authored the book “Topological Insulators”. In addition, he has been a recipient of a number of NSFC grants as a PI, including the Research Fund for International Excellent Young Scientists. Panagiotis was recognised as an Outstanding Reviewer for Journal of Physics: Condensed Matter in 2022, while more recently he won the Outstanding Referee Award of the American Physical Society which is a lifetime achievement.