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

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$d{e}_g$ 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.

7 pages, 5 figures

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