1. Ab initio calculation of low-energy collective charge-density excitations in MgB2
- Author
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Silkin, Viatcheslav M., Balassis, A., Echenique Landiribar, Pedro Miguel, and Tchoulkov Savkin, Evgueni Vladimirovich
- Subjects
ELECTRONIC, OPTICAL AND MAGNETIC MATERIALS ,charge density waves ,type II superconductors ,PHYSICS, CONDENSED MATTER ,density functional theory ,dielectric function ,magnesium compounds - Abstract
5 p., 4 figuras We present ab initio time-dependent density-functional theory calculation results for low-energy collective electron excitations in MgB2. The existence of a long-lived collective excitation corresponding to coherent charge density fluctuations between the boron sigma and pi bands (sigma pi mode) is demonstrated. This mode has a sine-like oscillating dispersion for energies below 0.5 eV. At even lower energy we find another collective mode (sigma sigma mode). We show the strong impact of local-field effects on dielectric functions in MgB2. These effects account for the long q-range behavior of the modes. We discuss the physics that these collective excitations bring to the energy region typical for lattice vibrations. Partial support from the University of the Basque Country (Grant No. GIC07IT36607), the Departamento de Educacion del Gobierno Vasco, and the Spanish Ministerio de Ciencia y Tecnologia (MCyT) (Grant No. FIS200766711C0101).
- Published
- 2009