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

A t-t'-J model has been employed to study the variation of the chemical pot ential shift with the change in the density of doped holes in high-if, cupr ates. 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-energ y approximation and U' --> infinity limit is taken to avoid double occupanc y. The Hamiltonian also includes the antiferromagnetic (AFM) exchange energ y (J). This term is treated within the mean-field approximation. The densit y of states (DOS) is calculated and it depends upon t, t, J and hole densit y n(H). It is found that the t-t'-J model is successful in explaining the d oping dependent DOS and the shift of the chemical potential with n(H) only in the overdoped regime of the La2-xSrxCuO4 system. For low and moderate do pings the agreement is not good. Reasons for the failure of the model for l ow doping regime are mentioned. (C) 1999 Elsevier Science B.V. All rights r eserved.