Influence of inter cell resonant tunneling on the out-of-plane electronic transport behavior in layered high T_c cuprates

Abstract

The influence of inter unit cell resonant tunneling between the copper-oxygen planes on the c-axis electronic conductivity (σ_c) in normal state of optimal doped bilayer high T_c cuprates like Bi₂Sr₂CaCu₂O_8+x is investigated using extended Hubbard Hamiltonian including resonant tunneling term (T₁₂) between the planes in two adjoining cells. The expression for the out-of-plane (c-axis) conductivity is calculated within Kubo formalism and single particle Green's function by employing Green's function equations of motion technique within meanfield approximation. On the basis of numerical computation, it is pointed out that the renormalized c-axis conductivity $(\tilde {\sigma}_{c})$ increases exponentially with the increment in inter cell resonant tunneling. The effect of T₁₂ on renormalized c-axis conductivity is found to be prominent at low temperatures as compared to temperatures above room temperature (~300 °K). The Coulomb correlation suppresses the variation of renormalized c-axis conductivity with temperature, while renormalized c-axis conductivity increases on increasing carrier concentration. These theoretical results are viewed in terms of existing c-axis transport measurements.