Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe 2 .

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 (WTe ₂ ). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe ₂ 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.