Theoretical investigation of pseudo-gap state of YBCO

TL;DR

This paper presents a theoretical study of the pseudo-gap state in YBCO using a mean field DDW Hamiltonian, revealing a first order transition and analyzing quantum oscillations.

Contribution

It introduces a self-consistent mean field approach to model the pseudo-gap state in YBCO as a DDW state, deriving thermodynamic properties and quantum oscillation estimates.

Findings

Pseudo-gap transition is first order.

Entropy per unit cell increases in the pseudo-gap state.

Quantum oscillation frequency estimated from fermion occupancy.

Abstract

A momentum space, mean field d-density wave (DDW) Hamiltonian is investigated self-consistently. The pseudo-gapped(PG)state of YBCO is assumed to correspond to the pure DDW state. A relation between thermodynamic potential of the system and certain spectral weight functions is established. This yields an expression for entropy in DDW state in the absence of magnetic field. The relation is useful for deriving finite temperature thermodynamics of the system. We show that the PG transition is a first order one and the entropy per unit cell increases in this state. We also analyze the fermion occupancy, in the presence of magnetic field, at the anti-nodal points of the Fermi surface to estimate the frequency of quantum oscillations.