The band structure and Fermi surface of La$_{0.6}$Sr$_{0.4}$MnO$_{3}$ thin films studied by in-situ angle-resolved photoemission spectroscopy

TL;DR

This study uses in-situ ARPES to investigate the electronic structure of La$_{0.6}$Sr$_{0.4}$MnO$_{3}$ thin films, revealing details about the Fermi surface and band structure that align with theoretical predictions but show narrower bandwidths and reduced spectral weight.

Contribution

First in situ ARPES analysis of La$_{0.6}$Sr$_{0.4}$MnO$_{3}$ thin films, providing detailed comparison with band-structure calculations and insights into discrepancies.

Findings

Observation of dispersive bands near $E_{F}$ indicating electron pockets.

Fermi surface size matches theoretical predictions.

Bandwidth narrower than predicted and spectral weight reduced.

Abstract

We have performed an in situ angle-resolved photoemission spectroscopy (ARPES) on single-crystal surfaces of La$_{0.6}$Sr$_{0.4}$MnO$_{3}$ (LSMO) thin films grown on SrTiO$_{3}$ (001) substrates by laser molecular beam epitaxy, and investigated the electronic structure near the Fermi level ($E_{F}$). The experimental results were compared with the band-structure calculation based on LDA + $U$. The band structure of LSMO thin films consists of several highly dispersive O 2$p$ derived bands in the binding energy range of 2.0 - 6.0 eV and Mn 3$d$ derived bands near $E_{F}$. ARPES spectra around the $Gamma$ point show a dispersive band near $E_{F}$ indicative of an electron pocket centered at the $Gamma$ point, although it was not so clearly resolved as an electronlike pocket due to the suppression of spectral weight in the vicinity of $E_{F}$. Compared with the band-structure calculation, the observed conduction band is assigned to the Mn 3$de_{g}$ majority-spin band responsible for the half-metallic nature of LSMO. We have found that the estimated size of the Fermi surface is consistent with the prediction of the band-structure calculation, while the band width becomes significantly narrower than the calculation. Also, the intensity near $E_{F}$ is strongly reduced. The origin of these discrepancies between the experiment and the calculation is discussed.