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

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 $\hat{I}{º}_0/T$ at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependence of $\hat{I}{º}_0/T$ 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.

5 pages, 4 figures