Anisotropies in insulating La$_{2-x}$Sr$_x$CuO$_4$: angular resolved photoemission and optical absorption

TL;DR

This paper investigates how orthorhombic lattice distortion and electron correlations in insulating La$_{2-x}$Sr$_x$CuO$_4$ cause anisotropies in electronic properties, affecting photoemission and optical absorption.

Contribution

It predicts that electron correlations significantly enhance anisotropic splitting between $a$ and $b$ hole valleys, impacting experimental observations.

Findings

Calculated hopping integral differences of about 8 meV.

Electron correlations amplify anisotropic effects in insulating phase.

Predicted distinct photoemission and optical absorption intensities at $a$ and $b$ points.

Abstract

Due to the orthorhombic distortion of the lattice, the electronic hopping integrals along the $a$ and $b$ diagonals, the orthorhombic directions, are slightly different. We calculate their difference in the LDA and find $t_{a}^{\prime}-t_{b}^{\prime}\approx 8 $meV. We argue that electron correlations in the insulating phase of La$_{2-x}$Sr$_{x}$CuO$_{4}$, i. e. at doping $x\leq 0.055,$ dramatically enhance the $(t_{a}^{\prime}-t_{b}^{\prime}) $-splitting between the $a$- and $b$-hole valleys. In particular, we predict that the intensity of both angle-resolved photoemission and of optical absorption is very different for the $a$ and $b$ nodal points.