Inhomogeneous reduction-annealing effects on the electron-doped cuprate superconductor revealed by micro-focused angle-resolved photoemission spectroscopy

TL;DR

This study uses micro-focused ARPES to reveal how inhomogeneous reduction-annealing affects the electronic structure and pseudogap behavior in electron-doped cuprate superconductors, highlighting spatial variations and their impact on superconductivity.

Contribution

It demonstrates the spatial inhomogeneity of electronic structures in PLCCO due to inhomogeneous annealing, linking pseudogap behavior to local electron concentration variations.

Findings

Significant spatial variation in Fermi surface observed.

Negative correlation between electron concentration and pseudogap magnitude.

Pseudogap opens abruptly with insufficient oxygen reduction.

Abstract

The development of the protect-annealing method has extended the superconductivity of the electron-doped cuprate Pr$_{1.3-x}$La$_{0.7}$Ce$_{x}$CuO$_{4}$ (PLCCO) into lower Ce concentrations, while the superconducting volume fraction decreases with underdoping. Employing angle-resolved photoemission spectroscopy with a micro-focused beam, we investigated the electronic structure of protect-annealed PLCCO ($x=0.08$) with small superconducting volume fraction. Significant spatial variation of Fermi surface area and shape was observed, suggesting inhomogeneity in electron concentrations and the pseudogap that competes with superconductivity. By performing measurements at dozens of different sample positions, negative and non-monotonic correlation was found between the electron concentration and pseudogap magnitude. The established correlation illustrates a systematic annealing dependence of the electronic structure where a pseudogap abruptly opens with insufficient oxygen reduction.