Theory of Pseudogap Phenomena in High-Tc Cuprates Based on the Strong Coupling Superconductivity

TL;DR

This paper explains the pseudogap phenomena in high-temperature cuprates as a result of strong coupling superconductivity, showing how pre-formed pairs and fluctuations suppress spectral weight and modify the electronic structure.

Contribution

It introduces a theoretical framework based on strong coupling superconductivity and T-matrix approximations to naturally explain pseudogap phenomena as precursor effects.

Findings

Superconducting fluctuations become propagative in strong coupling.

Spectral weight at the Fermi energy is strongly suppressed.

Pseudogap features arise from resonances with pre-formed pairs.

Abstract

In this paper we study the effects of the strong coupling superconductivity on the normal state electronic structure. We point out that the pseudogap phenomena in High-T_c cuprates are naturally explained as a precursor of the strong coupling superconductivity. We expand the reciprocal of the T-matrix with respect to the momentum and the frequency, and we discuss the properties of the expansion parameters. We estimate these parameters and carry out the calculations for the single particle self-energy using the T-matrix and the self-consistent T-matrix approximations, respectively. We show that the superconducting fluctuations, which are strongly diffusive within the conventional weak coupling theory, become propagative and have the character of the pre-formed pairs in the strong coupling case. The spectral weight and the density of states show the gap-like features by the effects of the resonances with the thermally excited weakly-damped pre-formed pairs. The spectral weight at the Fermi energy is strongly suppressed. This suppression starts at the mean field critical temperature $T_{MF}$ and the actual critical temperature T_c is strongly reduced owing to the fluctuations. These features properly explain to the pseudogap phenomena in High-T_c cuprates.