Quantum metric contribution to the pair mass in spin-orbit coupled Fermi superfluids

Abstract

As a measure of the quantum distance between Bloch states in the Hilbert space, the quantum metric was introduced to solid-state physics through the real part of the so-called geometric Fubini-Study tensor, the imaginary part of which corresponds to the Berry curvature measuring the emergent gauge field in momentum space. Here, we first derive the Ginzburg-Landau theory near the critical superfluid transition temperature, and then identify and analyze the geometric effects on the effective mass tensor of the Cooper pairs. By showing that the quantum metric contribution accounts for a sizeable fraction of the pair mass in a surprisingly large parameter regime throughout the BCS-BEC crossover, we not only reveal the physical origin of its governing role in the superfluid density tensor but also hint at its plausible roles in many other observables as well.