Lower Pseudogap Phase: A Spin/Vortex Liquid State

TL;DR

This paper proposes a new spin/vortex liquid state in the lower pseudogap phase of doped Mott insulators, characterized by spinon-vortex composites that influence transport properties and exhibit a finite correlation length.

Contribution

It introduces a detailed theoretical model of the lower pseudogap phase as a spin liquid with spinon-vortex composites, expanding understanding of pseudogap phenomena in high-Tc superconductors.

Findings

Identification of spinon-vortex composites as elementary excitations.

Explanation of Nernst effect and diamagnetism via spinon-vortices.

Quantitative phase diagram matching experimental observations.

Abstract

The pseudogap phase is considered as a new state of matter in the phase string model of the doped Mott insulator, which is composed of two distinct regimes known as upper and lower pseudogap phases, respectively. The former corresponds to the formation of spin singlet pairing and the latter is characterized by the formation of the Cooper pair amplitude and described by a generalized Gingzburg-Landau theory. Elementary excitation in this phase is a charge-neutral object carrying spin-1/2 and locking with a supercurrent vortex, known as spinon-vortex composite. Here thermally excited spinon-vortices destroy the phase coherence and are responsible for nontrivial Nernst effect and diamagnetism. The transport entropy and core energy associated with a spinon-vortex are determined by the spin degrees of freedom. Such a spontaneous vortex liquid phase can be also considered as a spin liquid with a finite correlation length and gapped S=1/2 excitations, where a resonancelike non-propagating spin mode emerges at the antiferromagnetic wavevector with a doping-dependent characteristic energy. A quantitative phase diagram in the parameter space of doping, temperature, and magnetic field is determined. Comparisons with experiments are also made.