Electron Pairing in Real Space,Model Pseudo-Spin Hamiltonian, and Ginzburg-Landau Equation for High-T_c Oxide Superconductors

抄録

Superconductivity by electron pairing in real space is modelled by a reduced Hamiltonian in pseudo-spin form, which is similar to the Hamiltonian for a planar Heisenberg ferromagnet in an external field. By making correspondence of coherent states of the model pseudo-spin system to superconducting states, an effective, zero-temperature Ginzburg-Landau (GL) equation is derived. Pseudo-spin parameters are evaluated from the GL parameters obtained by Meissner effect measurement and other methods for Ba₂YCu₃O_6.9 with T_c=91 K. The numerical value of T_c is estimated by using the mean-field approximation. The result so obtained is shown to be in fairly good agreement with the experimental result.