Influence of three site exchange interaction on the electronic spectra of doped bilayer high Tc cuprates

The influence of the three site exchange term (J3) on electronic spectral function A(k, ω) and density of states (DOS) is analyzed in doped bilayer high Tc cuprates in the normal state. The model Hamiltonian is based on the extended t-J-J3 model as derived from the Hubbard model under strong coupling limit so that it necessarily includes three site exchange term (J3). For the bilayer cuprates having two CuO2 planes in a unit cell, the coupling between the planes (t⊥) is also included. The expressions of A(k, ω) and DOS are obtained by employing the Green's function equation of motion technique within two sublattice approach and approximations applicable for strongly correlated systems. On the basis of numerical computation, we have found that three site exchange term (J3) affects the shape of the spectral function A(k, ω) and the DOS in optimal doped region of bilayer cuprates. The J3 term suppresses the bilayer splitting in the electronic spectra while enhances the DOS at Fermi level. The results are viewed in terms of recent ARPES measurement in bilayer cuprate in normal state.