Strongly Anisotropic s-Wave Gaps in Exotic Superconductors

Abstract

The exotic superconductors, defined as those which follow the phenomenological trend of Uemura (Tc approximately proportional to penetration depth^-2), presently constitute the most broad and general class of superconductors which can reasonably be considered "similar to the high-Tc cuprates". It is therefore of much interest to determine the forms of their pairing gap functions. We examine evidence for the gap forms in non-cuprate exotics, and demonstrate some general features. The cubic materials often have highly anisotropic gaps. The planar materials tend to have even stronger gap anisotropy, to the extent that they often have gap nodes, but nevertheless they usually have an s-wave-like gap symmetry. There is good evidence for the latter even in the controversial cases of planar organics and nickel borocarbides. Exceptions to these generalizations are also pointed out and discussed.

55 pages, to appear in Philosophical Magazine

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Cited by in corpus (7)

• Experimental evidence for a two-gap structure of superconducting NbSe_2: a specific heat study in external magnetic fields
• s-wave pairing in the optimally-doped LaO0.5F0.5BiS2 superconductor
• Comparative analysis of specific heat of YNi2B2C using nodal and two-gap models
• Pressure dependence of the upper critical field of MgB2 and of YNi2B2C
• Fermi-surface topology and the effects of intrinsic disorder in a class of charge-transfer salts containing magnetic ions, β''-(BEDT-TTF)_4[(H_3O)M(C_2O_4)_3]Y
• Field-induced quasiparticle excitations in novel type II superconductors
• Evidence for the Coexistence of Anisotropic Superconducting Gap and Nonlocal Effects in the Non-magnetic Superconductor LuNi2B2C