Fermi surface in La-based cuprate superconductors from Compton scattering imaging

TL;DR

This study uses high-resolution Compton scattering to image the Fermi surface in La-based cuprate superconductors, revealing nematicity-induced deformations and temperature-dependent pseudogap effects, challenging conventional views.

Contribution

It provides the first direct imaging evidence of nematicity-induced Fermi surface deformation in La-based cuprates using Compton scattering.

Findings

Fermi surface is strongly deformed by nematicity.

Temperature dependence suggests pseudogap formation.

Nematicity effects weaken with increased doping.

Abstract

Compton scattering provides invaluable information on the underlying Fermi surface (FS) and is a powerful tool complementary to angle-resolved photoemission spectroscopy and quantum oscillation measurements. Here we perform high-resolution Compton scattering measurements for La_{2-x}Sr_{x}CuO_{4} with x=0.08 (Tc=20K) at 300K and 150K, and image the momentum distribution function in the two-dimensional Brillouin zone. We find that the observed images cannot be reconciled with the conventional hole-like FS believed so far. Instead, our data imply that the FS is strongly deformed by the underlying nematicity in each CuO_2 plane, but the bulk FSs recover the fourfold symmetry. We also find an unusually strong temperature dependence of the momentum distribution function, which may originate from the pseudogap formation in the presence of the reconstructed FSs due to the underlying nematicity. Additional measurements for x=0.15 and 0.30 at 300K suggest similar FS deformation with weaker nematicity, which nearly vanishes at x=0.30.