Observing unconventional superconductivity via kinetic inductance in Weyl semimetal MoTe$_2$

Abstract

Identifying the pairing symmetry of unconventional superconductors plays an essential role in the ongoing quest to understand correlated electronic matter. A long-standing approach is to study the temperature dependence of the London penetration depth $\lambda$ for evidence of nodal points where the superconducting gap vanishes. However, experimental reports can be ambiguous due to the requisite low-temperature resolution, and the similarity in signatures of nodal quasiparticles and impurity states. Here we study the pairing symmetry of Weyl semimetal $T_d$-MoTe$_2$, where previous measurements of $\lambda$ have yielded conflicting results. We utilize a novel technique based on a microwave resontor to measure the kinetic inductance of MoTe$_2$, which is directly related to $\lambda$. The high precision of this technique allows us to observe power-law temperature dependence of $\lambda$, and to measure the anomalous nonlinear Meissner effect -- the current dependence of $\lambda$ arising from nodal quasiparticles. Together, these measurements provide smoking gun signatures of nodal superconductivity.