Nonequilibrium probe of paired electron pockets in the underdoped cuprates

TL;DR

This paper proposes an ARPES-based experimental method with a transport current to detect precursor pairing in the pseudogap phase of underdoped cuprates, aiming to clarify the nature of the pseudogap.

Contribution

It introduces a novel experimental approach using current-driven ARPES to identify paired electron pockets in the pseudogap regime of cuprates.

Findings

Weak currents tilt the paired band revealing the electron Fermi surface.

Stronger currents suppress pairing, exposing the Fermi surface.

Method is applicable to various reconstructed Fermi surfaces.

Abstract

We propose an experimental method that can be used generally to test whether the cuprate pseudogap involves precursor pairing that acts to gap out the Fermi surface. The proposal involves angular-resolved photoemission spectroscopy (ARPES) performed in the presence of a transport current driven through the sample. We illustrate this proposal with a specific model of the pseudogap that contains a phase-incoherent paired electron and unpaired hole Fermi surfaces. We show that even a weak current tilts the paired band and reveals parts of the previously gapped electron Fermi surface in ARPES if the binding energy is smaller but close to the pseudogap. Stronger currents can also reveal the Fermi surface through direct suppression of pairing. The proposed experiment is sufficiently general such that it can be used to reveal putative Fermi surfaces that have been reconstructed from other types of periodic order and are gapped out due to pairing. The observation of the predicted phenomena should help resolve the central question about the existence of pairs in the enigmatic pseudogap regime.