Doping dependence of coupling between charge carriers and bosonic modes in the normal state of high-Tc superconductors

Abstract

Recently, the doping dependence of the optical-conductivity scattering rate has been used by Hwang, Timusk, and Gu to gain some insight in the way the coupling between the charge carriers and the bosonic modes in high-Tc superconductors depends on doping. These authors used the extended Drude analysis, which does not take into account the normal-state pseudogap explicitly. In this work, we calculated the optical conductivity within the rotating antiferromagnetism theory, which models explicitly the pseudogap. Then we analyzed the resistivity as a function of temperature T and doping p. We extracted the scattering rate 1∕τ by fitting the La2−xSrxCuO4 resistivity data. We found that for p smaller than a critical value pc, 1∕τ shows a marginal-Fermi-liquid dependence for T greater than a p-dependent temperature Tρ*. But for T<Tρ*,1∕τ deviates downward from this law. We attribute this depression to a stronger coupling between the charge carriers and the normal-state bosonic modes. Both this coupling and Tρ* vanish at pc while superconductivity continues to be significant well above it. pc is interpreted as a quantum critical point, and Tρ* as the pseudogap temperature T* because it is found to agree with the experimental data on T*. We propose that a possible candidate for the bosonic modes may be the spin-wave excitations in the rotating frame of the rotating antiferromagnetic order.

Source-reported materials — not catalogue approval

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