Superfluid 3He and unconventional superconductors

The properties of superfluid He-3 as a well-studied model system of unconventional superfluidity are reviewed. This will include a discussion of BCS theory extended to spin triplet p-wave states, the nodal structure of the energy spectrum and its implications for the thermodynamic and transport properties. Similarities with the model states proposed for the heavy fermion and high T-c cuprate superconductors will be pointed out. Then, the existence of textures, vortices and other topological defects in the order parameter field of s-He-3 is discussed and contrasted with unconventional superconductivity in metals. Order parameter collective modes in s-He-3 and their possible counterparts in superconductors are considered. The role of the electric charge in superconductors and its coupling to the electromagnetic field will be analyzed. The last part will cover some recent results on nonlocal and nonlinear corrections to the magnetic penetration depth. (C) 1999 Elsevier Science B.V. All rights reserved.