The two colors of MgB2

Abstract

We present the anisotropic optical conductivity of MgB${}_2$ between 0.1 and 3.7 eV at room temperature obtained on single crystals of different purity by the spectroscopic ellipsometry and reflectance measurements. The bare (unscreened) plasma frequency ${\omega }_p$ is almost isotropic and equal to 6.3 eV, which contrasts some earlier reports of a very small value of ${\omega }_p$. The data suggests that the $\sigma$-bands are characterized by a stronger electron-phonon coupling ${\lambda }_{tr}$ but smaller impurity scattering ${\gamma }_{imp}$, compared to the $\pi$-bands. The optical response along the boron planes is marked by an intense interband transition at 2.6 eV, due to which the reflectivity plasma edges along the a- and c-axes are shifted with respect to each other. As a result, the sample spectacularly changes color from a blueish-silver to the yellow as the polarization is rotated from the in-plane direction towards the c-axis. The optical spectra are in good agreement with the published {\it ab initio} calculations. The remaining discrepancies can be explained by the relative shift of $\sigma$-bands and $\pi$-bands by about 0.2 eV compared to the theoretical band structure, in agreement with the de Haas-van Alphen experiments. The widths of the Drude and the interband peaks are both very sensitive to the sample purity.

11 pages, 13 figures

References in corpus (14)

• Kramers-Kronig constrained variational analysis of optical spectra
• Two-gap superconductivity in MgB${}_2$: clean or dirty?
• Vortex Imaging in the pi-Band of Magnesium Diboride
• Electronic Structure, Electron-Phonon Coupling, and Multiband Effects in MgB2
• Specific heat of single crystal MgB_2: a two-band superconductor with two different anisotropies
• Thermal conductivity of single crystalline MgB_2
• de Haas-van Alphen effect in single crystal MgB_2
• MgB2 single crystals: high pressure growth and anisotropic properties
• Fermi Surfaces of Diborides: MgB2 and ZrB2
• Specific heat of MgB_2 after irradiation
• Interpretation of the de Haas - van Alphen experiments in MgB2
• c-axis Raman Scattering in MgB2: Observation of a Dirty-Limit Gap in the pi-bands
• Clean and Dirty Superconductivity in Pure, Al doped, and Neutron Irradiated MgB2: a Far-Infrared Study
• Magneto-optical reflectivity of superconducting MgB2 single crystals

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