2005/09/15 by V. Guritanu, Alexey B. Kuzmenko, A. B. Kuzmenko +6
Materials Science · Physics and Astronomy · #Boron and Carbon Nanomaterials Research #Physics of Superconductivity and Magnetism #Superconductivity in MgB2 and Alloys #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.73.104509
published as Phys. Rev. B 73, 104509 (2006) · 11 pages, 13 figures
arxiv created 2005/09/15 · openalex publication_date 2006/03/17 · arxiv updated 2013/01/24 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
We present the anisotropic optical conductivity of MgB2 between 0.1 and 3.7\phantom\rule0.3em0exeV at room temperature obtained on single crystals of different purity by spectroscopic ellipsometry and reflectance measurements. The bare (unscreened) plasma frequency \ensuremathωp is almost isotropic and equal to 6.3\phantom\rule0.3em0exeV, which contrasts some earlier reports of a very small value of \ensuremathωp. The data suggests that the \ensuremathσ bands are characterized by a stronger electron-phonon coupling \ensuremathλtr but smaller impurity scattering \ensuremathγimp, compared to the \ensuremathπ bands. The optical response along the boron planes is marked by an intense interband transition at 2.6\phantom\rule0.3em0exeV, 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 toward the c axis. The optical spectra are in good agreement with the published ab initio calculations. The remaining discrepancies can be explained by the relative shift of \ensuremathσ bands and \ensuremathπ bands by about 0.2\phantom\rule0.3em0exeV 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.