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

TL;DR

This paper introduces a novel method combining ARPES with soft x-ray standing-wave excitation to study the electronic structure at buried interfaces, demonstrated on a magnetic tunnel junction, revealing depth-dependent electronic state variations.

Contribution

It presents SWARPES, a new technique for depth-resolved electronic structure analysis at buried interfaces, validated on a magnetic tunnel junction with theoretical comparison.

Findings

Distinct electronic behaviors at interface and bulk regions

Good agreement between experimental data and theoretical models

Potential for wide application in buried interface studies

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 La0.7Sr0.3MnO3/SrTiO3. Depth- and momentum-resolved maps of Mn 3d eg and t2g states from the central, bulk-like and interface-like regions of La0.7Sr0.3MnO3 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.