Superconductivity in time-reversal- symmetry-broken two-dimensional system: application to FeSe

量子物理学・ナノサイエンス第194回セミナー

概要

Monolayer FeSe on SrTiO₃, which exhibits high-temperature superconductivity, has recently been proposed to additionally possess (Néel) antiferromagnetic order. This magnetic order, however, breaks both inversion and time-reversal symmetry, the two symmetries guaranteeing a weak-coupling superconducting transition in three dimensions. Motivated by this finding, I will reexamine the minimal symmetries protecting superconductivity in two dimensions and the resulting order parameters. I will show that having a combination of either symmetry with a mirror operation on the basal plane is sufficient in two dimensions and discuss a minimal model with only one of the symmetries present. Finally, I will apply these considerations to the case of FeSe. Interestingly, despite having both combined symmetries, only one superconducting state is fully stable in antiferromagnetic FeSe, namely a chiral spin-triplet order, while any phonon-mediated s-wave order is strongly suppressed by the local ordered moments.

• 量子物理学・ナノサイエンス第194回セミナー

• ナノサイエンス・量子物理学国際研究センター 主催
• 東京工業大学理学院・物理学系、「ナノサイエンスを拓く量子物理学拠点」共催