SPring-8, the large synchrotron radiation facility

Date&Time: 5 September 2003 16:00-17:30

Speaker: Prof. Arun Bansil
Affiliation: Physics Department, Northeastern University

Abstract
　　Electron correlation effects are becoming an increasing focus of attention in understanding the behavior of wide classes of novel materials. This talk presents some of our recent work concerning several systems of current interest. In connection with the cuprate superconductors, we show how the Fermi surface evolves with electron doping in Nd2-xCexCuO4-delta as the Mott pseudogap collapses, in the light of recent high resolution ARPES experiments and related mean field Hartree-Fock and selfconsistent renormalization computations within the framework of the one-band t-t'-t''-U Hubbard model Hamiltonian. We also discuss how the ARPES matrix element via its selectivity properties can be exploited to focus on interesting physics in the cuprates (e.g. the issue of coherence effects and bilayer splitting in Bi2212). In connection with quantum dots, we discuss an exactly solvable model Hamiltonian for describing the interacting electron gas in a quantum dot. Results for a spherical square well confining potential are presented. The ground state is found to exhibit striking oscillations in spin polarization with dot radius at a fixed electron density. These oscillations are shown to induce characteristic signatures in the momentum density of the electron gas, providing a novel route for direct experimental observation of the dot magnetization via spectroscopies sensitive to the electron momentum density. Finally, brief comments are made on recent magnetic Compton scattering measurements on La1.2Sr1.8Mn207 from which we adduce that orbital effects on the momentum density in this CMR material are quite small.