Probing the Superconducting Order Parameter Symmetry in Monolayer WTe2*

Monolayer WTe2 exhibits a complex phase diagram, which includes the presence of superconductivity at low carrier densities adjacent to a quantum spin hall insulating phase. This provides a unique setting to explore the interplay between superconducting and topological insulating phases, where unconventional superconductivity is expected to emerge, potentially hosting p-wave or spin triplet pairing. Nevertheless, the symmetry of the superconducting order parameter remains unexplored. Here, we measure the complex conductivity of the complete phase diagram of WTe2 using microwave reflectometry measurements, allowing us to extract the temperature-dependent superfluid density while concurrently measuring the DC transport characteristics of the device. Our findings mark the initial steps toward understanding the pairing symmetry in WTe2 and provide insights into the quantum phase transition inherent to this material.