Theory of the quasi-particle spectra around a vortex in the two-dimensional t- J model

Abstract

In order to clarify the microscopic structure of vortex cores in high- T c superconductors, quasiparticle states are studied using the two-dimensional t- J model under a uniform magnetic field. The effect of strong correlation is taken into account via Gutzwiller approximation. The dependence on J/ t and the doping rate is discussed. The results show that an s-wave component is induced around the vortex core especially for the low-doping case. In the wide range of doping rate, the local density of states near the core center has a zero-energy peak, which is due to the d-wave superconductivity. In the low doping regime, however, the zero-energy peak splits into two levels, which reflects the s-wave component induced around the core. These results may explain the recent experimental results of scanning tunneling spectroscopy in YBa 2Cu 3O 7−δ.