Distinguishing finite momentum superconducting pairing states with two-electron photoemission spectroscopy

TL;DR

This paper demonstrates theoretically that two-electron photoemission spectroscopy can distinguish between different finite momentum superconducting pairing states, such as PDW and FFLO, by analyzing the counting rate to reveal the pairing's momentum and spin structure.

Contribution

It introduces a theoretical framework showing how 2e-ARPES can identify and differentiate finite momentum superconducting states based on their center-of-mass momentum and spin configurations.

Findings

2e-ARPES can directly reveal the momentum and spin of Cooper pairs.

The method distinguishes between d-wave, PDW, and FFLO phases.

It maps the momentum dependence of the superconducting order parameter.

Abstract

We show theoretically that double photoemission (2$e$-ARPES) may be used to identify the pairing state in superconductors in which the Cooper pairs have a nonzero center-of-mass momentum, ${\bf q}_{cm}$. We theoretically evaluate the 2$e$ ARPES counting rate, $P^{(2)}$, for the cases of a $d_{x^2-y^2}$-wave superconductor, a pair-density-wave (PDW) phase, and a Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase. We show that $P^{(2)}$ provides direct insight into the center-of-mass momentum and spin state of the superconducting condensate, and thus can distinguish between these three different superconducting pairing states. In addition, $P^{(2)}$ can be used to map out the momentum dependence of the superconducting order parameter. Our results identify 2$e$-ARPES as an ideal tool for identifying and probing ${\bf q}_{cm} \neq 0$ superconducting pairing states in superconductors.