Angular dependence of the upper critical field in the high-pressure 1T' phase of MoTe2

Superconductivity in the type-II Weyl semimetal candidate MoTe2 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 1T' phase to the low-temperature T-d phase is suppressed. Hence, applying pressure allows us to investigate the dimensionality of superconductivity in 1T'-MoTe2. We have performed a detailed study of the magnetotransport properties and upper critical field H-c2 of MoTe2 under pressure. The magnetoresistance (MR) and Hall coefficient of MoTe2 are found to decrease with increasing pressure. In addition, the Kohler's scalings for the MR data above similar to 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 Td to 1T' phase. The H-c2-temperature phase diagram constructed at 15 kbar, with H parallel to ab and H perpendicular to ab, can be satisfactorily described by the Werthamer-Helfand-Hohenberg model with the Maki parameters alpha similar to 0.77 and 0.45, respectively. The relatively large alpha may stem from a small Fermi surface and a large effective mass of semimetallic MoTe2. The angular dependence of H-c2 at 15 kbar can be well fit by the Tinkham model, suggesting the two-dimensional nature of superconductivity in the high-pressure 1T' phase.