Possible coexistence of nodal and nodeless pairing symmetry in superconducting 6R−SnNbSe2

Abstract

A possible route to realize fault-tolerant quantum computing is to find unconventional superconductors, where superconductivity coexists with nontrivial band topology. In this work, we report such a possibility in 6R−SnNbSe2 obtained by Sn intercalation into NbSe2. Rietveld refinement confirms a centrosymmetric crystal structure with space group R3¯m. Structural, electronic, and magnetic measurements confirm the emergence of a superconducting phase with a transition temperature Tc≈4 K. The temperature dependence of the upper critical field Hc2(T) is well described by a two-band model. Temperature-dependent magnetic penetration depth and superfluid density measurements are performed using the tunnel diode oscillator technique. Our analysis implies the mixing of nodal and nodeless order-parameter symmetry in 6R−SnNbSe2. Such results are surprising for a centrosymmetric superconductor but are consistent with theoretical predictions of topological nodal-line features in SnNbSe2. Thus, 6R−SnNbSe2 emerges as an interesting platform for exploring unconventional pairing mechanism in transition metal dichalcogenide superconductors.

Source-reported materials — not catalogue approval

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