Enhancement of superconductivity coexisting with charge density wave in lattice expanded ${\text{NbTe}}_2$

Abstract

We report a significant enhancement of superconducting transition temperature (${\text{T}}_{\text{c}}$) of transition metal dichalcogenide (TMD) superconductor ${\text{NbTe}}_2$ from 0.56 K to 2.8 K. Detailed x-ray structure analysis reveals that our ${\text{T}}_{\text{c}}$-enhanced sample has an anisotropic lattice distortion inducing ~1% expansion of the unit cell volume and multi-domain formation in the $\text{ab}$ planes. Despite the unit cell expansion, the distorted 1T structure, closely related to the charge density wave (CDW) order in this material, persists. Hall measurements show almost identical behaviors for both samples indicating that electronic structure does not change much due to the unit cell expansion. These results suggest that the CDW still coexists with the enhanced superconductivity unlike the other TMD superconductors.