 Unconventional superconductor

An unconventional superconductor realizes unconventional superconductivity: its pairing cannot be described by the simple conventional isotropic spin-singlet model. The precise usage should be stated, since unconventional gap symmetry and an unconventional microscopic pairing mechanism are different claims.

A d-wave superconductor supplies a concrete example. Its superconducting gap function changes sign with momentum direction and can vanish at nodes, permitting low-energy Bogoliubov quasiparticles. Nodal quasiparticle power laws probe those excitations, while a phase-sensitive test of d-wave pairing probes the relative gap signs. An unusual superconducting transition temperature alone does not establish a particular pairing symmetry, and a real d-wave gap does not automatically imply broken time reversal.