Signatures of the topological s(+−) superconducting order parameter in the type-II Weyl semimetal T(d)-MoTe(2)

In its orthorhombic T (d) polymorph, MoTe(2) is a type-II Weyl semimetal, where the Weyl fermions emerge at the boundary between electron and hole pockets. Non-saturating magnetoresistance and superconductivity were also observed in T (d)-MoTe(2). Understanding the superconductivity in T (d)-MoTe(2), which was proposed to be topologically non-trivial, is of eminent interest. Here, we report high-pressure muon-spin rotation experiments probing the temperature-dependent magnetic penetration depth in T (d)-MoTe(2). A substantial increase of the superfluid density and a linear scaling with the superconducting critical temperature T (c) is observed under pressure. Moreover, the superconducting order parameter in T (d)-MoTe(2) is determined to have 2-gap s-wave symmetry. We also exclude time-reversal symmetry breaking in the superconducting state with zero-field μSR experiments. Considering the strong suppression of T (c) in MoTe(2) by disorder, we suggest that topologically non-trivial s (+−) state is more likely to be realized in MoTe(2) than the topologically trivial s (++) state.