Superconducting density of states and vortex cores of 2H-NbS2

TL;DR

This study uses STM/S to explore the superconducting density of states and vortex structures in 2H-NbS2, revealing unique features and vortex core states that differ from related compounds, enhancing understanding of its superconducting properties.

Contribution

It provides the first detailed STM/S analysis of 2H-NbS2's superconducting density of states and vortex core features, highlighting differences from similar materials.

Findings

Distinct features at 0.97 meV and 0.53 meV in the density of states

Hexagonal vortex lattice with localized core states

Absence of charge density wave order and star-shaped vortex pattern

Abstract

Scanning tunneling microscopy and spectroscopy (STM/S) measurements in the superconducting dichalcogenide 2H-NbS2 show a peculiar superconducting density of states with two well defined features at 0.97 meV and 0.53 meV, located respectively above and below the value for the superconducting gap expected from single band s-wave BCS model (D=1.76kBTc=0.9 meV). Both features have a continuous temperature evolution and disappear at Tc = 5.7 K. Moreover, we observe the hexagonal vortex lattice with radially symmetric vortices and a well developed localized state at the vortex cores. The sixfold star shape characteristic of the vortex lattice of the compound 2H-NbSe2 is, together with the charge density wave order (CDW), absent in 2H-NbS2.