Type-II superconductivity in the Dirac semimetal PdTe2

TL;DR

This study reveals that the Dirac semimetal PdTe2 exhibits type-II superconductivity with a fully gapped s-wave order parameter, and demonstrates that disorder can switch its superconducting type from I to II.

Contribution

It provides the first detailed microscopic characterization showing PdTe2 as a type-II superconductor and highlights the role of disorder in altering its superconducting properties.

Findings

PdTe2 is a type-II superconductor with a flux line lattice.

Superconductivity in PdTe2 is fully gapped and s-wave symmetric.

Disorder can induce a transition from type-I to type-II superconductivity.

Abstract

We report on the microscopic superconducting properties of the Dirac semimetal PdTe2. In this study, we have focused on mosaic crystals of PdTe2, and used detailed zero field and transverse field muon spin relaxation/rotation ($\mu$SR), ac-magnetic susceptibility, and resistivity measurements to investigate their superconducting properties. The magnetic susceptibility measurements reveal two superconducting transition temperatures at 1.8 and 1.6~K, respectively, in agreement with earlier reports. In contrary to these reports, we find that these mosaic PdTe2 crystals, are not type-I, but rather type-II superconductors. In fact, we observe the clear manifestation of a flux line lattice through a clear diamagnetic shift and Gaussian broadening of the Fourier spectra in the superconducting state. This behavior is likely caused by the disorder in the mosaic crystals of PdTe2 studied here. Our analysis of the superconducting order parameter by the means of temperature dependent magnetic penetration depth $\lambda(T)$ reveals a fully gapped superconducting state that can be well-fitted using an s-wave symmetric gap. We find that PdTe2 is a promising model system for the investigation and interplay of non-trivial topology, surface superconductivity, and type-II bulk superconductivity in a van-der-Waals material. Moreover, our results indicate that the superconductivity in this material can be easily modified from type-I to type-II by disorder in the system.