Coexistence of Nodal and Nodeless Pairing Symmetry in Superconducting 6R-SnNbSe2

TL;DR

This study reports the synthesis of a new non-centrosymmetric superconductor, 6R-SnNbSe2, which exhibits coexistence of nodal and nodeless pairing, suggesting potential for unconventional topological superconductivity.

Contribution

It introduces a novel polytype of Sn-intercalated NbSe2 with mixed pairing symmetry, expanding the understanding of superconductivity in non-centrosymmetric transition-metal dichalcogenides.

Findings

Superconductivity observed below 4 K in 6R-SnNbSe2.

Evidence of coexistence of nodal and nodeless pairing symmetries.

Potential topological superconducting properties due to non-centrosymmetric structure.

Abstract

Majorana fermions, a fundamental idea to fault-tolerant quantum computing, can emerge in systems where superconductivity coexists with nontrivial band topology. One promising route to realizing such topological superconductors (TSCs) involves inducing superconductivity in topological materials, particularly in systems lacking inversion symmetry. In this study, we report the synthesis and detailed characterization of Sn-intercalated NbSe2, forming a new polytype, 6R-SnNbSe2. This compound crystallizes in the non-centrosymmetric space group R3m and exhibits bulk superconductivity below Tc around 4 K. Structural, electronic, and magnetic measurements confirm the emergence of a superconducting phase derived from Sn intercalation into the non-superconducting 3R-NbSe2. Temperature-dependent magnetic penetration depth and superfluid density measurements down to 1.5 K are performed using the tunnel diode oscillator technique. The findings suggest the mixing of nodal and nodeless superconductivity in 6R-SnNbSe2. Given the non-centrosymmetric nature of the crystal structure and the theoretical prediction of topological nodal-line features in SnNbSe2, it is an interesting candidate to investigate unconventional pairing mechanisms. Our findings highlight the potential of this material to host nontrivial superconducting states among the transition-metal dichalcogenides.