Berezinskii-Kosterlitz-Thouless Transition in Spin-Charge Separated Superconductor

TL;DR

This paper introduces a 2D model of spin-charge separated superconductivity showing a Berezinskii-Kosterlitz-Thouless transition, with phase boundaries matching experimental oxide superconductor diagrams.

Contribution

It presents a novel theoretical model coupling spinon and holon phases with a gauge field, revealing a BKT transition in spin-charge separated superconductors.

Findings

BKT-type phase transition observed in the model.

Gauge-field excitations are gapless.

Phase diagram shape agrees with experiments.

Abstract

A model for spin-charge separated superconductivity in two dimensions is introduced where the phases of the spinon and holon order parameters couple gauge-invariantly to a statistical gauge-field representing chiral spin-fluctuations. The model is analyzed in the continuum limit and in the low-temperature limit. In both cases we find that physical electronic phase correlations show a superconducting-normal phase transition of the Berezinskii-Kosterlitz-Thouless type, while statistical gauge-field excitations are found to be strictly gapless. The normal-to-superconductor phase boundary for this model is also obtained as a function of carrier density, where we find that its shape compares favorably with that of the experimentally observed phase diagram for the oxide superconductors.