Suppression of both superconductivity and structural transition in hole-doped MoTe$_2$ induced by Ta substitution

TL;DR

This study investigates how Ta hole-doping in MoTe$_2$ suppresses both the structural transition and superconductivity, challenging previous assumptions that suppressing structural transition enhances superconductivity.

Contribution

It reveals that in hole-doped MoTe$_2$, suppression of the structural transition does not lead to increased superconductivity, contrasting with electron-doped cases.

Findings

Both $T_s$ and $T_c$ decrease with Ta doping.

Hall coefficient peaks where $T_s$ is suppressed.

Carrier concentration influences $T_c$ tuning.

Abstract

Type-II Weyl semimetal MoTe$_2$ exhibits a first-order structural transition at $T_s$ $\sim$250~K and superconducts at $T_c$ $\sim$0.1~K at ambient pressure. Both $T_s$ and $T_c$ can be manipulated by several tuning parameters, such as hydrostatic pressure and chemical substitution. It is often reported that suppressing $T_s$ enhances $T_c$, but our study shows a different behaviour when MoTe$_2$ is hole-doped by Ta. When $T_s$ is suppressed by Ta doping, $T_c$ is also suppressed. Our findings suggest that the suppression of $T_s$ does not necessarily enhance superconductivity in MoTe$_2$. By connecting with the findings of electron-doped MoTe$_2$, we argue that varying electron carrier concentration can effectively tune $T_c$. In addition, the Hall coefficient is enhanced around the doping region, where $T_s$ is completely suppressed, suggesting that the critical scattering around the structural transition may also play a role in suppressing $T_c$.