Theory of the unusual doping and temperature dependence of photoemission spectra in manganites

¹  Centre for Condensed Matter Theory (CCMT), Department of Physics, Indian Institute of Science Bangalore 560012, India
²  Harishchandra Research Institute - Allahabad 211019, India
³  Department of Physics and Astronomy, University of British Columbia - 6224, Agricultural Road, Vancouver, BC V6T 1Z1, Canada
⁴  Solid State and Structural Chemistry Unit, Indian Institute of Science - Bangalore 560012, India
⁵  Jawaharlal Nehru Centre for Advanced Scientific Research - Bangalore 560064, India
⁶  Center for Advanced Materials, Indian Association for Cultivation of Science - Kolkata 700032, India
⁷  Department of Physics, Banaras Hindu University - Varanasi 221005, India

Corresponding author: prabs@mri.ernet.in

Received: 28 February 2008
Accepted: 6 April 2008

Abstract

A recent, major, puzzle in the core-level photoemission spectra of doped manganites is the observation of a 12 eV wide shoulder with intensity varying with temperature T as the square of the magnetization over a T scale of order 200 K, an order of magnitude less than electronic energies. This is addressed and resolved here, by extending a recently proposed two-fluid polaronmobile electron model for these systems to include core-hole effects. The position of the shoulder is found to be determined by Coulomb and Jahn-Teller energies, while its spectral weight is determined by the mobile electron energetics which is strongly T and doping dependent, due to annealed disorder scattering from the polarons and the t core spins. Our theory accounts quantitatively for the observed T dependence of the difference spectra, and furthermore, explains the observed correspondence between spectral changes due to increasing doping and decreasing T.