High-temperature cuprate superconductors studied by x-ray Compton scattering and positron annihilation spectroscopies

TL;DR

This study uses x-ray Compton scattering and positron annihilation spectroscopies to investigate the electronic structure and defect roles in high-temperature cuprate superconductors, revealing the Fermi surface and dopant effects.

Contribution

It demonstrates the application of x-ray Compton scattering to observe the Fermi surface and explores positron annihilation spectroscopy for defect analysis in cuprates.

Findings

Fermi surface observed in overdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$

Dopant Sr atoms influence electronic structure

Positron annihilation reveals oxygen defect roles

Abstract

The bulk Fermi surface in an overdoped ($x = 0.3$) single crystal of La$_{2-x}$Sr$_{x}$CuO$_{4}$ has been observed by using x-ray Compton scattering. This momentum density technique also provides a powerful tool for directly seeing what the dopant Sr atoms are doing to the electronic structure of La$_2$CuO$_{4}$. Because of wave function effects, positron annihilation spectroscopy does not yield a strong signature of the Fermi surface in extended momentum space, but it can be used to explore the role of oxygen defects in the reservoir layers for promoting high temperature superconductivity.