Donostia International Physics Center，西班牙

摘要：

Electron–phonon coupling (EPC) is central to conventional superconductivity. In this talk, we present recent insights into two distinct superconducting systems—LaRu₃Si₂ and MgB₂—with a focus on how lattice symmetry, flat-band physics, and quantum geometry govern their superconducting properties.

LaRu₃Si₂ (Tc=7.8K) is a kagome metal recently reported to exhibit charge density wave (CDW) order above room temperature. Our findings reveal that the EPC in LaRu₃Si₂ is highly mode-selective, dominated by the strong interactions between Ru-B3u phonons and Ru-Ag electrons within the kagome lattice. Light hole doping significantly enhances the superconducting critical temperature Tc by 50%, whereas heavy doping triggers structural instability and ferromagnetism. Furthermore, we perform high-throughput screening and identify 3063 stable materials in the kagome 1:3:2 family, of which 428 are predicted to exhibit superconductivity with Tc > 1 K and the highest Tc reaching 15 K.

MgB2, a well-established superconductor with Tc=39K, is revisited from a symmetry-driven perspective. We demonstrate that its electronic, phononic, and electron-phonon properties can be understood with minimal inputs from ab initio. The obstructed sp² bonds generate a compact σ Fermi surface with large quantum geometry, naturally favoring strong EPC. We further show that electron doping raises the Fermi level toward the degenerate nodal point of this Fermi surface, enhancing Tc despite a reduced density of states—highlighting the pivotal role of quantum geometry in optimizing superconductivity.

参考文献：

[1] Deng J, Jiang Y, Cerqueira T F T, et al. Theory of Superconductivity in LaRu3Si2 and Predictions of New Kagome Flat Band Superconductors[J]. arXiv preprint arXiv:2503.20867 (2025)

地点：中国科学院物理研究所M楼830