Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 22: Unconventional Superconductors
TT 22.12: Talk
Wednesday, September 7, 2022, 18:30–18:45, H10
Two bands Ising superconductivity from Coulomb interactions in monolayer NbSe2 — Sebastian Hörhold, Juliane Graf, •Magdalena Marganska, and Milena Grifoni — Institute for Theoretical Physics, University of Regensburg, Germany
The nature of superconductivity in monolayer transition metal dichalcogenides is still object of debate. It has already been argued that repulsive Coulomb interactions, combined with the disjoint Fermi surfaces around the K,K’ valleys and at the Γ point, can lead to superconducting instabilities in monolayer NbSe2. Here, we demonstrate the two bands nature of superconductivity in NbSe2. In our approach it arises from repulsive Coulomb interactions, long range (resulting in intravalley scattering) and short range (intervalley scattering), together with Ising spin-orbit coupling. The two distinct superconducting gaps, one for the upper and one for the lower spin-orbit splitted band, both consist of a mixture of s-wave and f-wave components. Using a microscopic multiband BCS approach, we derive and self-consistently solve the gap equation, demonstrating the stability of nontrivial solutions in a realistic parameter range. The temperature dependence of the gaps and of the critical in-plane field are consistent with various sets of existing experimental data. Our results, although derived for NbSe2, are however universal and apply to almost all systems with disjoint Fermi surfaces connected by two competing scattering processes.