Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe2

In conventional superconductors an external magnetic field generally suppresses superconductivity. This results from a simple thermodynamic competition of the superconducting and magnetic free energies. In this study, we report the unconventional features in the superconducting epitaxial thin film tungsten telluride (WTe2). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe2 thin films with a high precision rotation stage, we map the upper critical field H-c2 at different temperatures T. We observe the superconducting transition temperature T-c is enhanced by in-plane magnetic fields. The upper critical field H-c2 is observed to establish an unconventional non-monotonic dependence on temperature. We suggest that this unconventional feature is due to the lifting of inversion symmetry, which leads to the enhancement of H-c2 in Ising superconductors.