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

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Compton scattering is a key technique for probing electron momentum distributions.
• Understanding the Fermi surface (FS) is crucial for explaining electronic properties of materials.
• La$_{2-x}$Sr$_{x}$CuO$_{4}$ is a high-temperature superconductor with complex electronic phases.

Purpose of the Study:

• To investigate the Fermi surface (FS) of La$_{2-x}$Sr$_{x}$CuO$_{4}$ using high-resolution Compton scattering.
• To explore the influence of nematicity on the FS and its temperature dependence.
• To compare experimental findings with existing models of the electronic structure.

Main Methods:

• High-resolution Compton scattering measurements were performed on La$_{2-x}$Sr$_{x}$CuO$_{4}$ samples.
• Momentum distribution functions were imaged in the two-dimensional Brillouin zone.
• Measurements were conducted at various temperatures (300 K and 150 K) and doping levels (x = 0.08, 0.15, 0.30).

Main Results:

• Compton scattering data contradict the conventional hole-like Fermi surface (FS) model.
• The FS is significantly deformed by nematicity within CuO$_{2}$ planes, while bulk FSs maintain fourfold symmetry.
• A strong temperature dependence of the momentum distribution suggests pseudogap formation linked to reconstructed FSs.

Conclusions:

• Nematicity plays a critical role in deforming the Fermi surface of La$_{2-x}$Sr$_{x}$CuO$_{4}$.
• The findings necessitate a revision of current understanding of the electronic structure in this material.
• The interplay between nematicity, pseudogap, and Fermi surface reconstruction is highlighted.