Superconductivity in kagome metals due to soft loop-current fluctuations

by Prof. Jörg Schmalian (Karlsruhe Institute of Technology)

Monday 25 Aug 2025, 10:30 → 11:30 Asia/Shanghai

Tsung-Dao Lee Institute/N4F-N400 - meeting room (Tsung-Dao Lee Institute)

Tencent meeting link:  https://meeting.tencent.com/dm/4nVW2VmeRcNR

Meeting ID:  770121729, no password

 

Abstract:

We demonstrate that soft fluctuations of translation symmetry-breaking loop currents provide a mechanism for unconventional superconductivity in kagome metals that naturally addresses the multiple superconducting phases observed under pressure. Focusing on the rich multi-orbital character of these systems, we show that loop currents involving both vanadium and antimony orbitals generate low-energy collective modes that couple efficiently to electrons near the Fermi surface and mediate attractive interactions in two distinct unconventional pairing channels. While loop-current fluctuations confined to vanadium orbitals favor chiral d+id superconductivity, which spontaneously breaks time-reversal symmetry, the inclusion of antimony orbitals stabilizes an s± state that is robust against disorder. We argue that these two states are realized experimentally as pressure increases and the antimony-dominated Fermi surface sheet undergoes a Lifshitz transition.

 

Biography:

Jörg Schmalian received his doctoral degree in 1993 at the Freie University in Berlin. He has contributed about 250 scholarly articles to the peer reviewed literature and given more than 400 invited talks at international conferences. At the Karlsruhe Institute of Technology (KIT) he is the head of the Institute for Theory of Condensed Matter (TKM). His research group at TKM works on strongly correlated electron systems and complex quantum matter. He also heads the division Theory of Quantum Materials at the Institute for Quantum Materials and Technologies (IQMT) at KIT. Prior to moving to Karlsruhe in 2011, Dr. Schmalian was a full professor at Iowa State University and Senior Scientists at the Department of Energy Ames Laboratory. Schmalian serves on a number of international advisory boards, has co-organized numerous international conferences, workshops and summer schools, and has been honored by several awards, including a fellowship from the American Physical Society, the 2022 John Bardeen Prize for superconductivity theory, the 2023 Physics-Award Dresden. He is a member of the Heidelberg Academy of Sciences.