The Physics Behind High-Temperature Superconducting Cuprates: The "Plain Vanilla" Version Of RVB

TL;DR

This paper revisits the RVB theory of high-temperature cuprate superconductivity using renormalized mean field theory, explaining key phenomena like the pseudogap, nodal quasiparticles, and spin-charge separation, emphasizing superexchange as the pairing mechanism.

Contribution

It applies the renormalized mean field theory to explain experimental observations in cuprates, highlighting the role of superexchange over phonons in d-wave superconductivity.

Findings

Explains the pseudogap and nodal quasiparticles.

Accounts for large renormalizations of superfluid density.

Supports superexchange as the pairing mechanism.

Abstract

One of the first theoretical proposals for understanding high temperature superconductivity in the cuprates was Anderson's RVB theory using a Gutzwiller projected BCS wave function as an approximate ground state. Recent work by Paramekanti, Randeria and Trivedi has shown that this variational approach gives a semi-quantitative understanding of the doping dependences of a variety of experimental observables in the superconducting state of the cuprates. In this paper we revisit these issues using the ``renormalized mean field theory'' of Zhang, Gros, Rice and Shiba based on the Gutzwiller approximation in which the kinetic and superexchange energies are renormalized by different doping-dependent factors $g_{t}$ and $g_{S}$ respectively. We point out a number of consequences of this early mean field theory for experimental measurements which were not available when it was first explored, and observe that it is able to explain the existence of the pseudogap, properties of nodal quasiparticles and approximate spin-charge separation, the latter leading to large renormalizations of the Drude weight and superfluid density. We use the Lee-Wen theory of the phase transition as caused by thermal excitation of nodal quasiparticles, and also obtain a number of further experimental confirmations. Finally, we remark that superexchange, and not phonons, are responsible for d-wave superconductivity in the cuprates.