Paramagnetic-like destructive mechanism against superconductivity in Sr 2RuO 4: a triplet scenario versus a singlet one
Abstract
The most popular description of superconductivity phenomenon in Sr 2RuO 4 is based on a so-called single-band (usually γ-band) “isotropic p-wave order parameter”. In a magnetic field parallel to the conducting planes, such triplet “isotropic p-wave phase” is not destroyed by the Clogston-Chandrasekhar paramagnetic limiting field and can be destroyed only the Meissner currents (i.e., the orbital effects). We analyze the orbital destructive effects agains superconductivity for in-plane magnetic field (when electron orbits are open) and find that Hc2∥(0)≃0.75T(dHc2∥(T)/dT) (which is a little bigger than the Werthamer-Helfand-Hohenberg value for an isotropic 3D case). We point out that the experimentally determined ratio Hc2∥(0)/T(≃0.44-0.5 in Sr 2RuO 4 is significantly less than the calculated value 0.75. Since the upper critical field, Hc2∥(T), is a well experimentally defined quantity in Sr 2RuO 4 (unlike high-T c superconductors) we conclude that the single-band triplet “isotropic p-wave order parameter” seems to be inappropriate description of superconductivity in this material. Two possibilities are discussed: 1) Three-band nature of triplet superconductivity; 2) Singlet (d-wave) nature of superconducting pairing (in this case, the destructive actions of both the orbital effects and the Clogston-Chandrasekhar paramagnetic effects result in an agreement with the experimentally observed value of Hc2∥(0)/T(.
- Publication:
-
Physica C Superconductivity
- Pub Date:
- November 2000
- DOI:
- 10.1016/S0921-4534(00)00932-1
- Bibcode:
- 2000PhyC..341.1677L