Electronic spectra of doped bilayer high Tc cuprates within t–t′–t″–t⊥–U model

We present the calculation of the electronic spectral function and density of states (DOS) in the underdoped and optimal doped bilayer high Tc cuprates (like Bi2Sr2CaCu2O8+x) in normal state. We have used the tight binding extended Hubbard Hamiltonian containing next-nearest-neighbour hopping (t′), second next-nearest-neighbour hopping (t″) along with the momentum dependent interlayer coupling parameter for two CuO2 planes per unit cell system. To obtain the expressions of single particle spectral function A(k, ω) and DOS, we have used Green’s function equations of motion approach within semi-classical approximation due to Kishore [R. Kishore, Phys. Rev. B 35 (1987) 6854]. It is pointed out through our numerical analysis that t′ shifts the A(k, ω) away from the Fermi level with increasing sharpness and provides favourable conditions for the bilayer splitting effects in the electronic spectra of bilayer cuprates. On the other hand the effect of second next-nearest-neighbour hopping (t″) is just opposite to that of t′ and opposes the bilayer splitting effects. The Coulomb energy U also plays an important role in the shape of spectral function at Fermi level. The DOS is suppressed at the Fermi level in underdoped region with two peak structure and in optimal doped region, a finite DOS emerges at the Fermi level with the evolution of third peak structure. The variation of A(k, ω) and DOS are found to be in qualitative agreement with the recent ARPES measurements in bilayer cuprates.