Effects of three-dimensional band structure in angle- and spin-resolved photoemission from half-metallic La2/3Sr1/3MnO3

We present an angle- and spin-resolved photoemission study of half-metallic three-dimensional perovskite La2/3Sr1/3MnO3 thin films grown with pulsed laser deposition. The experiments are performed in the (100) mirror plane. The experimental results are related to GGA+U calculations through simulations of photoemission spectra, which take into account the final state broadening in surface-perpendicular momentum and the initial-state broadening in energy. We demonstrate that due to the three-dimensional nature of La2/3Sr1/3MnO3, these intrinsic mechanisms of the photoemission process give rise to deviations of the photoemission spectrum from the spectral function corresponding to the strict momentum conservation. In the spin-integrated data, we identify ghost spectral intensity coming from states with different momenta and, in particular, nonvanishing intensity filling the whole interior of the central Fermi surface spheroid. In the spin-resolved data, we find experimental polarization values near the Fermi surface of 55% at the normal emission and 80% at off-normal emission. Despite a seeming contradiction to the half-metallic picture, such a reduction in spin contrast is reproduced by our simulations as a result of the broadening mechanisms and is consistent with the half-metallic nature of La2/3Sr1/3MnO3.