| speaker: | H.R. Krishnamurthy Bangalore, India |
| time: | Tu., 14.08, 16:00-17:00 |
A recent, major, puzzle in the core-level photoemission spectra of doped manganites is the observation of a 1-2 eV wide shoulder with intensity varying with temperature T as the square of the magnetization over a T scale of order 200K, an order of magnitude less than electronic energies. In this talk I discuss a recent theory we have developed* to address and resolve this puzzle, by extending the recently proposed (localized-polaron + mobile-electron) two fluid model for manganites to include core-hole effects. The shoulder seems to arise from a broadened X-ray edge singularity whose exponent varies with temperature, reflecting the rapid redistribution of the spectral density of the mobile electrons due to their strong scattering from thermally disordered t2g core spins. Furthermore, our theory leads to a correspondence between spectral changes due to increasing doping and decreasing temperature, as experimentally observed.
(* work done in collaboration with Prabuddha Sanyal, Subhra Sen Gupta, Nandan Pakhira, D. D. Sarma and T. V. Ramakrishnan.)