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MM: Fachverband Metall- und Materialphysik
MM 25: Electronic properties II
MM 25.4: Vortrag
Mittwoch, 28. März 2007, 15:30–15:45, H6
Is black phosphorous really a semiconductor? — •Alim Ormeci and Helge Rosner — Max-Planck-Institut CPfS, Dresden
Black phosphorous in the A17 orthorhombic structure (space group 64) is known to be a narrow-band-gap semiconductor (Eg = 0.3 eV) at ambient pressure. However, our recent electronic structure calculations based on various state-of-the-art first-principles, all-electron, full-potential codes have revealed that there is actually no gap in the electronic band structure of black phosphorous! Both LDA and GGA calculations give one small electron, and one small hole pocket around the k-point corresponding to 2 π / b along the longest orthorhombic axis b. Thus, according to these very accurate calculations black phosphorous should be a compensated (semi)metal with very small N(EF) values in a wide range of unit cell volumes, at least between 0.90 V0 and 1.15 V0, where V0 is the ambient pressure volume. The finding that the computed Fermi surface areas are very small has both computational and experimental implications. On the computational side, very fine sampling of the Brillouin zone is necessary in order to have a correct and converged result. On the experimental side, the implied low carrier concentration may introduce complications. We suggest new experiments such as photoemission, conductivity and de Haas-van Alphen measurements, to be performed on very pure, well-characterized single crystals of black phosphorous for testing the prediction regarding the existence of these small Fermi surfaces.
DFG Emmy Noether Programm is acknowledged for support.