Universality of the Electronic Structure from a Half Filled CuO_2 Plane

TL;DR

This study demonstrates that the low energy electronic structure of half-filled cuprates is universal across different compounds and independent of the apical atom, revealing intrinsic features of these materials through ARPES data.

Contribution

The paper provides experimental evidence that the electronic structure in insulating cuprates is universal and unaffected by apical atom variations, using photon energy dependent ARPES analysis.

Findings

Electronic dispersion is photon energy independent.

Asymmetry in electron occupation is robust across photon energies.

D-wave-like dispersion in insulators deviates from simple d-wave form near nodal points.

Abstract

We present angle resolved photoemission (ARPES) data from insulating A_2CuO_2X_2 (A=Sr, Ca; X=Cl, Br), Sr_2Cu_3O_4Cl_2, and Bi_2Sr_2MCu_2O_8 (M=Er, Dy) single crystals which illustrate that the low energy electronic structure of the half-filled cuprates are independent of the apical atom. By performing a photon energy dependent study on Ca_2CuO_2Cl_2 we are able to distinguish between features which are intrinsic and those which are a result of the photoemission matrix elements. We find that the dispersion is independent of photon energy, while an asymmetry in the electron occupation probability across the antiferromagnetic zone boundary is robust to variations in photon energy. Finally, we show that the d-wave-like dispersion which exists in the insulator along the antiferromagnetic zone boundary does not precisely fit the simple d-wave functional form near the nodal direction.