Study of doping-dependent shift in the chemical potential of high T_c cuprates by t-t'-J model

Abstract

A t-t'-J model has been employed to study the variation of the chemical potential shift with the change in the density of doped holes in high-T_c cuprates. The model Hamiltonian incorporates the nearest neighbour hopping, the next nearest-neighbour hopping and a fictitious Coulomb interaction (U'). The fictitious Coulomb interaction is treated within the Hubbard self-energy approximation and U'→∞ limit is taken to avoid double occupancy. The Hamiltonian also includes the antiferromagnetic (AFM) exchange energy (J). This term is treated within the mean-field approximation. The density of states (DOS) is calculated and it depends upon t, t, J and hole density n_H. It is found that the t-t'-J model is successful in explaining the doping dependent DOS and the shift of the chemical potential with n_H only in the overdoped regime of the La_2-xSr_xCuO₄ system. For low and moderate dopings the agreement is not good. Reasons for the failure of the model for low doping regime are mentioned.