Dielectric functions and collective excitations in MgB_2

Abstract

The frequency- and momentum-dependent dielectric function $\epsilon (\mathbf{q},\omega )$ as well as the energy loss function Im[-${\epsilon }^{-1}(\mathbf{q},\omega )$\protect{]} are calculated for intermetallic superconductor $Mg{B}_2$ by using two {\it ab initio} methods: the plane-wave pseudopotential method and the tight-binding version of the LMTO method. We find two plasmon modes dispersing at energies $\sim 2$-8 eV and $\sim 18$-22 eV. The high energy plasmon results from a free electron like plasmon mode while the low energy collective excitation has its origin in a peculiar character of the band structure. Both plasmon modes demonstrate clearly anisotropic behaviour of both the peak position and the peak width. In particular, the low energy collective excitation has practically zero width in the direction perpendicular to boron layers and broadens in other directions.

3 pages with 10 postscript figures. Submitted to PRB on May 14 2001

References in corpus (12)

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Cited by in corpus (5)

• Superconducting properties of MgB2 from first principles
• Low-Energy Charge-Density Excitations in MgB${}_2$: Striking Interplay between Single-Particle and Collective Behavior for Large Momenta
• Ab initio calculation of low-energy collective charge-density excitations in MgB2
• Tuning MgB_2(0001) surface states
• Effect of interband interactions of phonon and charge fluctuation on superconducting parameters of MgB2