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

TL;DR

This study demonstrates that expanding the lattice of NbTe₂ enhances its superconducting transition temperature from 0.56 K to 2.8 K, while maintaining charge density wave order, indicating coexistence of superconductivity and CDW.

Contribution

It reveals that lattice expansion can significantly boost superconductivity in NbTe₂ without disrupting charge density wave order, a novel insight into TMD superconductors.

Findings

Superconducting T_c increased from 0.56 K to 2.8 K.

Lattice expansion induces ~1% unit cell volume increase.

Charge density wave persists despite lattice distortion.

Abstract

We report a significant enhancement of superconducting transition temperature ($\textit{T}_\textrm{c}$) of transition metal dichalcogenide (TMD) superconductor $\textrm{NbTe}_2$ from 0.56 K to 2.8 K. Detailed x-ray structure analysis reveals that our $\textit{T}_\textrm{c}$-enhanced sample has an anisotropic lattice distortion inducing ~1% expansion of the unit cell volume and multi-domain formation in the $\textit{ab}$ 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.