A 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 parameterizations 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 displays for both systems long-range Friedel oscillations alternating in sign. Upon scaling, the oscillation pattern becomes universal, with the periodic features 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.
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