Universal route to chiral Ising superconductivity in monolayer TaS2 and NbSe2

Abstract

We investigate Ising superconductivity in two archetypal intrinsic superconductors, monolayer 1H−TaS2 and 1H−NbSe2, in a bottom-up approach. Using ab initio-based tight-binding parametrizations for the relevant low-energy d bands, the screened interaction is evaluated microscopically in a scheme including Bloch overlaps. In direct space, the screened potential for both systems displays long-range Friedel oscillations alternating in sign. Upon scaling, the oscillation pattern becomes universal, with the location of minima and maxima locked to the lattice. Solving the momentum-resolved gap equations, a chiral ground state with p-like symmetry is generically found. Due to the larger Ising spin-orbit coupling, the chiral gap is more anisotropic in TaS2 than in NbSe2. This is reflected in tunneling spectra displaying V-shaped features for the former, in quantitative agreement with low-temperature scanning tunneling experiments on TaS2. At the same time, our results reconcile the apparent discordance with hard gap tunneling spectra reported for the sibling NbSe2.

Source-reported materials — not catalogue approval

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