The physics behind high-temperature superconducting cuprates: the  plain vanilla  version of RVB

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.

Staggered Flux State in Two-Dimensional Hubbard Models

“…in the metallic phase under pressure, namely, pseudogap behavior is absent. 78 Furthermore, similar pseudogap behavior was observed in a hole-doped κ-ET salt [κ-(ET) 4 Hg 2.89 Br 8 ], 79 in which the doping rate is 0.11 and t ′ /t ∼ 0.8. With these experimental results in mind, we study the SF state on an anisotropic triangular lattice in the framework applied to the frustrated square lattice for cuprates.…”

“…1,2 Because the pseudogap phase appears in the proximity of half filling, it is probably related to Mott insulators 3,4 (precisely, charge-transfer insulators 5 ). Experimentally, the pseudogap phase presents various features distinct from an ordinary Fermi liquid.…”

“…Experimentally, the pseudogap phase presents various features distinct from an ordinary Fermi liquid. 3,4 (1) A large gap different from the d x 2 −y 2 -wave SC (d-SC) gap opens in the spin degree of freedom near the momenta of (π, 0) and (0, π). (2) However, the material is conductive and does not have a charge gap.…”

“…2,20 (3) Charge orders or charge density waves are observed in resonant X-ray scattering experiments. [21][22][23] (4) (π, π)-folded (shadow) bands appear in ARPES spectra, and so forth. [24][25][26][27] Note, however, that the thermodynamic properties such as specific heat and spin susceptibility have not provided any evidence of the phase transition.…”

Study on Unconventional Superconductivity after the BCS Paradigm

“…In this case, the spin singlet pairs are naturally formed yielding a highly fluctuating quantum RVB state. [41] This is certainly a very interesting picture which may get an indirect support from the very strong superconducting fluctuation, or residual Copper pairs in the normal state far above T c . The convincing evidence for this RVB state is still lacking.…”