Multiband nodeless superconductivity near the charge-density-wave quantum critical point in ZrTe3-xSex

TL;DR

This study investigates the superconducting properties of ZrTe$_{3-x}$Se$_x$ near the charge-density-wave quantum critical point, revealing multiple nodeless gaps and conventional superconductivity through thermal conductivity measurements.

Contribution

It provides the first evidence of multigap nodeless superconductivity in ZrTe$_{3-x}$Se$_x$ near the CDW QCP, clarifying the nature of superconductivity in this system.

Findings

Negligible residual linear thermal conductivity indicates nodeless gaps.

Field dependence shows multigap superconductivity.

Superconductivity remains conventional despite proximity to CDW QCP.

Abstract

Recently it was found that selenium doping can suppress the charge-density-wave (CDW) order and induce bulk superconductivity in ZrTe$_3$. The observed superconducting dome suggests the existence of a CDW quantum critical point (QCP) in ZrTe$_{3-x}$Se$_x$ near $x \approx$ 0.04. To elucidate its superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe$_{3-x}$Se$_x$ single crystals ($x$ = 0.044 and 0.051) down to 80 mK. For both samples, the residual linear term $\kappa_0/T$ at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependence of $\kappa_0/T$ manifests multigap behavior. These results demonstrate multiple nodeless superconducting gaps in ZrTe$_{3-x}$Se$_x$, which indicates conventional superconductivity despite of the existence of a CDW QCP.