Observation of multiple Zhang-Rice excitations in a correlated solid: Resonant inelastic X-ray scattering study of Li₂CuO₂

¹  Department of Physics, Boston University - 590 Commonwealth Ave., Boston, MA 02215, USA
²  School of Physics, Trinity College Dublin - Dublin 2, Ireland
³  Physics Department, Macquarie University - NSW 2109, Australia
⁴  Department of Physics, Uppsala University - Box 530, S-75121, Uppsala, Sweden
⁵  Advanced Light Source, Lawrence Berkeley National Laboratory - Berkeley, CA 94720, USA
⁶  Center for Materials Science and Engineering, Massachusetts Institute of Technology - Cambridge, MA 02139, USA

Corresponding author: ksmith@bu.edu

Received: 19 January 2007
Accepted: 2 July 2007

Abstract

Multiple Zhang-Rice type spectral features have been observed in resonant inelastic X-ray scattering (RIXS) from the quasi–one-dimensional cuprate charge transfer insulator Li₂CuO₂. The first feature appears at constant emission energy, and is associated with a Zhang-Rice singlet final state. The second is an interplaquette charge transfer excitation that results in a novel triplet Zhang-Rice–type final state. It is accompanied by the presence of a O 2p nonbonding to upper Hubbard band excitation at an energy close to that of a calculated triplet charge transfer Zhang-Rice–type excitation. The site selectivity and polarization rules associated with RIXS allows these two excitations to be distinguished.