title: Ab initio investigation of collective charge excitations in MgB2.
abstract: A sharp collective charge excitation is predicted in MgB2 at approximately 2.5 eV for q perpendicular to the boron layers, based on an all-electron analysis of the dynamical density response within time-dependent density functional theory. This novel excitation, consisting of coherent charge fluctuation between Mg and B sheets, induces an abrupt plasma edge in the experimentally observable reflectivity. The existence of this mode reflects the unique electronic structure of MgB2 that is also responsible for strong electron-phonon coupling. By contrast, the acoustic plasmon, recently suggested to explain the high T(c), is not realized when realistic transition strengths are incorporated.
authors.affiliation: Physics Department, University of California, Davis, California 95616, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Ku
authors.forename: W E
authors.initials: WE
authors.lastname: Pickett
authors.forename: R T
authors.initials: RT
authors.lastname: Scalettar
authors.forename: A G
authors.initials: AG
authors.lastname: Eguiluz