Elucidating the Band Gap of Niobium Dioxide

ORAL

Abstract

Like VO$_{\mathrm{2}}$, niobium dioxide (NbO$_{\mathrm{2}})$ belongs to the family of transition metal oxides with a temperature-driven metal-to-insulator transition. However, NbO$_{\mathrm{2}}$ has received considerably less attention, and several open questions about the material remain. One such question, of both practical and fundamental importance, is the nature and size of the band gap in the low-temperature, distorted rutile phase with a range reported for the gap of 0.5 eV to 1.2 eV. In this work, we investigate the low-temperature phase, utilizing several methodologies - density functional theory within the standard local density approximation (LDA), LDA$+$U, hybrid functional, and the GW approximation, to better understand the physics of the band gap in NbO$_{\mathrm{2}}$. Comparisons of the calculations are made to recent experimental work on NbO$_{\mathrm{2}}$ utilizing photoemission spectroscopy and ellipsometry. This work is supported by DOE under the SciDAC program, the NSF, and SRC.

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Authors

  • Andy O'Hara

    The University of Texas at Austin, University of Texas at Austin

  • Derek Vigil-Fowler

    University of California - Berkeley and Lawrence Berkeley National Lab

  • Steven G. Louie

    University of California at Berkeley, Lawrence Berkeley National Lab, University of California - Berkeley and Lawrence Berkeley National Lab, Department of Physics, University of California at Berkeley; Materials Sciences Divisions, Lawrence Berkeley National Laboratory, Univ of California - Berkeley and Lawrence Berkeley National Lab, Department of Physics, UC Berkeley and Lawrence Berkeley National Lab, University of California, Berkeley and Lawrence Berkeley National Laboratory, University of California at Berkeley and Lawrence Berkeley National Laboratory, UC Berkeley and Lawrence Berkeley National Lab, University of California at Berkeley and Lawrence Berkeley National Lab, Physics Department, UC Berkeley and Lawrence Berkeley National Lab, Department of Physics, University of California, Berkeley, and Materials Science Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA, UC Berkeley physics/ LBNL MSD

  • Alexander Demkov

    The University of Texas at Austin, The University of Texas, Univ of Texas, Austin, University of Texas at Austin