Electronic properties of GeTe and Ag- or Sb-substituted GeTe studied by low-temperature Te125 NMR
Year: 2016
Type: article
Abstract: We have carried out $^{125}\mathrm{Te}$ nuclear magnetic resonance (NMR) in a wide temperature range of 1.5--300 K to investigate the electronic properties of ${\mathrm{Ge}}_{50}{\mathrm{Te}}_{50},\phantom{\rule{0.16em}{0ex}}{\mathrm{Ag}}_{2}{\mathrm{Ge}}_{48}{\mathrm{Te}}_{50}$, and ${\mathrm{Sb}}_{2}{\mathrm{Ge}}_{48}{\mathrm{Te}}_{50}$ from a microscopic point of view. From the temperature dependence of the NMR shift $(K)$ and nuclear spin lattice relaxation rate $(1/{T}_{1})$, we found that two bands contribute to the physical properties of the materials. One band overlaps the Fermi level providing the metallic state where no strong electron correlations are revealed by Korringa analysis. The other band is separated from the Fermi level by an energy gap of ${E}_{\mathrm{g}}/{k}_{\mathrm{B}}\ensuremath{\sim}67$ K, which gives rise to semiconductorlike properties. First-principles calculation reveals that the metallic band originates from the Ge vacancy while the semiconductorlike band is related to the fine structure of the density of states near the Fermi level. Low-temperature $^{125}\mathrm{Te}$ NMR data for the materials studied here clearly show that Ag substitution increases hole concentration while Sb substitution decreases it.
Authors: J. Cui, E. M. Levin, Y. Lee, Y. Furukawa
Institutions: Iowa State University, Ames National Laboratory
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2464228852