Orbital Fulde-Ferrell-Larkin-Ovchinnikov state in 2H-NbS2 flakes

TL;DR

This paper reports the discovery of an orbital FFLO state in 2H-NbS2 flakes, demonstrating layer-dependent finite-momentum pairing in a TMDC superconductor, which is more robust against magnetic fields and depends on flake thickness.

Contribution

It extends the observation of orbital FFLO states to 2H-NbS2, highlighting the role of weak interlayer coupling in stabilizing this state at higher temperatures and lower magnetic fields.

Findings

Orbital FFLO state observed in 2H-NbS2 flakes.

Weak interlayer coupling stabilizes FFLO state.

FFLO state persists at higher temperatures and lower fields.

Abstract

Symmetry breaking in a layered superconductor with Ising spin-orbit coupling has offered an opportunity to realize unconventional superconductivity. To be more specific, orbital Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, exhibiting layer-dependent finite-momentum pairing, may emerge in transition metal dichalcogenides materials (TMDC) in the presence of an in-plane magnetic field. Orbital FFLO state can be more robust against the magnetic field than the conventional superconducting state with zero-momentum pairing. This feature renders its potential in field-resilient superconducting functionality. Although, orbital FFLO state has been reported in NbSe2 and MoS2, it is not yet clear if orbital FFLO state can be extended to other TMDC superconductor. Here, we report the observation of orbital FFLO state in 2H-NbS2 flakes and its dependence on the thickness of flake. We conclude that the relatively weak interlayer coupling is instrumental in stabilizing orbital FFLO state at higher temperature with respect to the critical temperature and lower magnetic field with respect to paramagnetic limit in NbS2 in comparison to its NbSe2 counterpart.