Zero-bias conductance peak in detached flakes of superconducting 2H-TaS${}_2$ probed by scanning tunneling spectroscopy

Abstract

We report an anomalous tunneling conductance with a zero bias peak in flakes of superconducting 2H-TaS${}_2$ detached through mechanical exfoliation. To explain the observed phenomenon, we construct a minimal model for a single unit cell layer of superconducting 2H-TaS${}_2$ with a simplified 2D Fermi surface and sign-changing Cooper pair wavefunction induced by Coulomb repulsion. Superconductivity is induced in the central $\Gamma$ pocket, where it becomes nodal. We show that weak scattering at the nodal Fermi surface, produced by non-perturbative coupling between tip and sample, gives Andreev states that lead to a zero bias peak in the tunneling conductance. We suggest that reducing dimensionality down to a few atom thick crystals could drive a crossover from conventional to sign changing pairing in the superconductor 2H-TaS${}_2$.

arXiv comment8 pages, 4 figures

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• Evidence of nodal superconductivity in monolayer 1H-TaS${}_2$ with hidden order fluctuations
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• Nonlinear optical responses in multi-orbital topological superconductors
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