Momentum-resolved electronic structure at a buried interface from soft X-ray standing-wave angle-resolved photoemission

¹ Department of Physics, University of California Davis - Davis, CA 95616, USA
² Materials Sciences Division, Lawrence Berkeley National Laboratory - Berkeley, CA 94720, USA
³ Stanford Institute for Materials and Energy Science, Stanford University and SLAC National Accelerator Laboratory 2575 Sand Hill Road, Menlo Park, CA 94029, USA
⁴ Department of Chemistry, Physical Chemistry Institute, Ludwig-Maximilians University-Munich - Münich, Germany
⁵ Peter-Grünberg-Institut PGI-6, Forschungszentrum Jülich GmbH - 52425 Jülich, Germany
⁶ Faculty of Science and Technology, MESA + Institute for Nanotechnology, University of Twente - Enschede, The Netherlands
⁷ Advanced Light Source, Lawrence Berkeley National Laboratory - Berkeley, CA 94720, USA
⁸ IBM Almaden Research Center - San Jose, CA 95120, USA
⁹ Max-Planck-Institut für Mikrostrukturphysik - Weinberg 2, D-06120 Halle (Saale), Germany
¹⁰ National Center for Electron Microscopy, Lawrence Berkeley National Laboratory - Berkeley, CA 94720, USA
¹¹ Department of Earth and Environmental Sciences and Center of Nanoscience (CENS), Ludwig-Maximilians University-Munich - Münich, Germany

Received: 12 September 2013
Accepted: 4 October 2013

Abstract

Angle-resolved photoemission spectroscopy (ARPES) is a powerful technique for the study of electronic structure, but it lacks a direct ability to study buried interfaces between two materials. We address this limitation by combining ARPES with soft X-ray standing-wave (SW) excitation (SWARPES), in which the SW profile is scanned through the depth of the sample. We have studied the buried interface in a prototypical magnetic tunnel junction La_0.7Sr_0.3MnO₃/SrTiO₃. Depth-and momentum-resolved maps of Mn 3d e_g and t_2g states from the central, bulk-like and interface-like regions of La_0.7Sr_0.3MnO₃ exhibit distinctly different behavior consistent with a change in the Mn bonding at the interface. We compare the experimental results to state-of-the-art density-functional and one-step photoemission theory, with encouraging agreement that suggests wide future applications of this technique.