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TT: Fachverband Tiefe Temperaturen

TT 75: Low Dimensional Systems

TT 75.11: Vortrag

Donnerstag, 21. März 2024, 17:45–18:00, H 3007

Superconductivity and the normal state quantum geometry in two-dimensional superconductors — •Florian Simon, Louis Pagot, Marc Gabay, and Mark-Oliver Goerbig — Laboratoire de Physique des Solides, Université Paris-Saclay, Orsay, France

Superconductivity has, since 1911, become a pillar and a flagship of condensed matter physics. The main paradigm is given by BCS theory which, in its standard form, consists of quasiparticles in a single, partially filled band, pairing and thus condensating in a collective dissipationless state. This single band approximation has its limits. Indeed, since the 1980s, physicists have come to realize that in a multiband setting, even adiabatic, each band will carry an influence of the other bands in the form of two geometric quantities, namely the Berry curvature and the quantum metric. These quantities form what we call band/quantum geometry. In the context of superconductivity, this means that even if a single band is involved in the Cooper pairing, it can carry a quantum geometry if the normal state (NS) has more than one band. The influence of this NS quantum geometry on the superconducting state is the subject of this talk. On one side, we study the influence of the NS Berry curvature on BCS theory in the context of two-dimensional massive Dirac fermions. We find that it generally lowers the critical temperature, in a quantifiable way. On another side, we consider the two-dimensional (111) LaAlO₃/SrTiO₃ interface. Our results suggest that the quantum metric has a sizeable role in the appearance of superconducting domes in this interface, as a function of gate voltage.

Keywords: Two-dimensional superconductivity; Geometrical and topological phases; Berry curvature; Quantum metric; Transition Metal Dichalcogenides