# Angular dependence of the upper critical field in the high-pressure $1T'$ phase of MoTe$_2$

## TL;DR

This study investigates how pressure affects the superconducting properties and electronic structure of MoTe$_2$, revealing a transition to two-dimensional superconductivity in the high-pressure 1$T'$ phase.

## Contribution

It provides detailed measurements of the upper critical field and magnetotransport under pressure, demonstrating the 2D nature of superconductivity in high-pressure MoTe$_2$.

## Key findings

- Superconductivity in MoTe$_2$ becomes more two-dimensional at high pressure.
- Fermi surface reconstruction occurs during the structural transition.
- The upper critical field fits the Tinkham model indicating 2D superconductivity.

## Abstract

Superconductivity in the type-II Weyl semimetal candidate MoTe$_2$ has attracted much attention due to the possible realization of topological superconductivity. Under applied pressure, the superconducting transition temperature is significantly enhanced, while the structural transition from the high-temperature 1$T'$ phase to the low-temperature $T_d$ phase is suppressed. Hence, applying pressure allows us to investigate the dimensionality of superconductivity in 1$T'$-MoTe$_2$. We have performed a detailed study of the magnetotransport properties and upper critical field $H_{c2}$ of MoTe$_2$ under pressure. The magnetoresistance (MR) and Hall coefficient of MoTe$_2$ are found to be decreasing with increasing pressure. In addition, the Kohler's scalings for the MR data above $\sim$11 kbar show a change of exponent whereas the data at lower pressure can be well scaled with a single exponent. These results are suggestive of a Fermi surface reconstruction when the structure changes from the $T_d$ to 1$T'$ phase. The $H_{c2}$-temperature phase diagram constructed at 15 kbar, with $H\parallel ab$ and $H\perp ab$, can be satisfactorily described by the Werthamer-Helfand-Hohenberg model with the Maki parameters $\alpha \sim$ 0.77 and 0.45, respectively. The relatively large $\alpha$ may stem from a small Fermi surface and a large effective mass of semimetallic MoTe$_2$. The angular dependence of $H_{c2}$ at 15 kbar can be well fitted by the Tinkham model, suggesting the two-dimensional nature of superconductivity in the high-pressure 1$T'$ phase.