Unconventional superconductivity

Superconductivity in materials without inversion symmetry (NCS) in the respective crystal structures occurs in the presence of an antisymmetric pin-orbit coupling as a consequence of an emerging electric field gradient. The superconducting condensate is then a superposition of spin-singlet and spin-triplet Cooper pairs. This scenario accounts for various experimental findings such as nodes in the superconducting gap or extremely large upper critical magnetic fields found in superconductors like CePt3Si or CeRhSi3.
Spin-triplet pairing can occur in a NCS environment in spite of Anderson's theorem that spin-triplet pairing requires a crystal structure that exhibits inversion symmetry. A central issue that arises when debating physical properties of NCS superconductors pertains the role of strong correlations among electrons.