We report the high-field superconducting properties of thin, disordered Re films via magneto-transport and tunneling density of states measurements. Films with thicknesses in the range of 9 nm to 3 nm had normal state sheet resistances of ∼0.2 kΩ to ∼1 kΩ and corresponding transition temperatures in the range of 6 K to 3 K. Tunneling spectra were consistent with those of a moderate coupling BCS superconductor. Notwithstanding these unremarkable superconducting properties, the films exhibited an extraordinarily high upper critical field. We estimate their zero-temperature Hc2 to be more than twice the Pauli limit. Indeed, in 6 nm samples the estimated reduced critical field Hc2/Tc∼ 5.6 T/K is among the highest reported for any elemental superconductor. Although the sheet resistances of the films were well below the quantum resistance RQ=h/4e2, their Hc2's approached the theoretical upper limit of a strongly disordered superconductor for which kFℓ∼1.
@article{arxiv.2010.07674,
title = {Extreme High-Field Superconductivity in Thin Re Films},
author = {F. N. Womack and D. P. Young and D. A. Browne and G. Catelani and J. Jiang and E. I. Meletis and P. W. Adams},
journal= {arXiv preprint arXiv:2010.07674},
year = {2021}
}