SUPERCONDUCTIVITY IN THE 2-DIMENSIONAL T-J MODEL AT LOW ELECTRON-DENSITY

The two-dimensional t-J model at low electron densities is unstable against various forms of electron pairing at low enough temperatures. At parameter values J/t much less than 1, the leading instability, although only at very low temperature, is to p-wave pairing similar to the Hubbard model. At values of J/t > 1, an instability against d-wave pairing sets in at a higher temperature as found numerically by Dagotto and co-workers. In addition, at values of J/t > 2, which are beyond the threshold for a bound state in the low-electron-density limit, a region of predominantly s-wave pairing is found.