Probing emergent excitations with middle-energy electron energy loss spectroscopy

¹ Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences - Ningbo, Zhejiang 315201, China
² Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences Beijing 100049, China
³ Department of Physics and Astronomy, Rutgers University - Piscataway, NJ 08854, USA

^(a) ywcao@nimte.ac.cn

Received: 29 August 2019
Accepted: 9 December 2019

Abstract

Probing the emergent excitations in a range of is fundamentally important to understand a variety of emergent phenomena in quantum materials, however, the characterization techniques of which are very limited at present. Here, we take high-temperature superconducting YBa₂Cu₃O_7−δ films () as an archetype to demonstrate the powerful capabilities of middle-energy electron energy loss spectroscopy (EELS) in determining the emergent excitations. Three dominative features (2.9, 12.9, and 25 eV) are observed in the EELS spectra, one of which is a newly observed peak near 2.9 eV resulting from excitations between the Zhang-Rice state and the upper Hubbard band. Moreover, incident energy-dependent EELS spectra indicate that the signals of these three features are strongly dependent on the energy of incident electrons. Our work provides a route to probe emergent excitations in the energy range with utilizing high-resolution two-dimensional energy and momentum mapping.