Manifestations of Symmetry and Internal Phases in Unconventional Superconductors
Abstract
A study of unconventional superconductivity is presented. The general Ginzburg-Landau approach based on the broken symmetry is reviewed. By introducing the coupling between the antiferromagnetic and superconducting ordering which belongs to the ^1E _{rm g} representation of the D_{rm 4h} group, we obtain nine possible phase diagrams of the heavy fermion superconductor URu_2Si _2 in the H-T plane. The domain wall formed by two time reversed states of the mixture order parameter belonging to A_{rm 1g} +/- iB_{rm 1g} representation of the tetragonal group results in a weak superconducting region which acts as a barrier against the current flow by having a lower critical density than bulk. The orientation dependence of the Josephson current is studied. The current passing through the bicrystalline grain boundaries is investigated as a function of misalignment angle. The current decreases as the misalignment angle increases in general. Symmetry-restricted form of transport coefficient tensors is tabulated for multi-dimensional order parameters of the tetragonal and hexagonal systems. A brief discussion of superconducting fluctuations is given in the appendix.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1992
- Bibcode:
- 1992PhDT.......152B
- Keywords:
-
- HIGH TEMPERATURE SUPERCONDUCTORS;
- Physics: Condensed Matter