Upper Pseudogap Phase: Magnetic Characterizations

TL;DR

This paper proposes that the upper pseudogap phase in high-Tc cuprates is due to spin singlet pairing within a bosonic RVB framework, supported by magnetic property calculations and phase diagram analysis.

Contribution

It introduces a bosonic RVB-based model explaining the UPP, linking magnetic properties, doping, temperature, and magnetic field effects, and discusses the phase diagram and charge properties.

Findings

Strong spin correlations develop in the UPP.

Magnetic properties show enhancement at (,) and suppression at (0,0).

A relation between critical magnetic field H_{PG} and temperature T0 is established.

Abstract

It is proposed that the upper pseudogap phase (UPP) observed in the high-Tc cuprates correspond to the formation of spin singlet pairing under the bosonic resonating-valence-bond (RVB) description. We present a series of evidence in support of such a scenario based on the calculated magnetic properties including uniform spin susceptibility, spin-lattice and spin-echo relaxation rates, which consistently show that strong spin correlations start to develop upon entering the UPP, being enhanced around the momentum (\pi, \pi) while suppressed around (0, 0). The phase diagram in the parameter space of doping concentration, temperature, and external magnetic field, is obtained based on the the bosonic RVB theory. In particular, the competition between the Zeeman splitting and singlet pairing determines a simple relation between the "critical" magnetic field, H_{PG}, and characteristic temperature scale, T0, of the UPP. We also discuss the magnetic behavior in the lower pseudogap phase at a temperature Tv lower than T0, which is characterized by the formation of Cooper pair amplitude where the low-lying spin fluctuations get suppressed at both (0, 0) and (\pi, \pi). Properties of the UPP involving charge channels will be also briefly discussed.