Bulk two-dimensional Pauli-limited superconductor

Abstract

We present a nearly perfect Pauli-limited critical-field phase diagram for the anisotropic organic superconductor $\ensuremath{\alpha}\text{\ensuremath{-}}{(\text{ET})}_{2}{\text{NH}}_{4}{(\text{SCN})}_{4}$ when the applied magnetic field is oriented parallel to the conducting layers. The critical fields $({H}_{{c}_{2}})$ were found by use of penetration depth measurements. Because ${H}_{{c}_{2}}$ is Pauli limited, the size of the superconducting energy gap can be calculated. The role of spin-orbit scattering and many-body effects play a role in explaining our measurements.