Unusual 209Bi NMR quadrupole effects in topological insulator Bi2Se3

Robin Guehne; Vojtěch Chlan; Grant V M Williams; Shen V Chong; Kazuo Kadowaki; Andreas Pöppl; Jürgen Haase

doi:10.1016/j.jmr.2019.03.008

Unusual ²⁰⁹Bi NMR quadrupole effects in topological insulator Bi₂Se₃

J Magn Reson. 2019 May:302:34-42. doi: 10.1016/j.jmr.2019.03.008. Epub 2019 Mar 29.

Authors

Robin Guehne¹, Vojtěch Chlan², Grant V M Williams³, Shen V Chong⁴, Kazuo Kadowaki⁵, Andreas Pöppl⁶, Jürgen Haase⁷

Affiliations

¹ Felix Bloch Institute for Solid State Physics, University of Leipzig, Linnstrasse 5, 04103 Leipzig, Germany; The MacDiarmid Institute for Advanced Materials and Nanotechnology, SCPS, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand; Robinson Research Institute, Victoria University of Wellington, PO Box 33436, Lower Hutt 5046, New Zealand.
² Charles University in Prague, Faculty of Mathematics and Physics, V HoleA˚ovikch 2, 180 00 Prague 8, Czech Republic.
³ The MacDiarmid Institute for Advanced Materials and Nanotechnology, SCPS, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand.
⁴ The MacDiarmid Institute for Advanced Materials and Nanotechnology, SCPS, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand; Robinson Research Institute, Victoria University of Wellington, PO Box 33436, Lower Hutt 5046, New Zealand.
⁵ Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
⁶ Felix Bloch Institute for Solid State Physics, University of Leipzig, Linnstrasse 5, 04103 Leipzig, Germany.
⁷ Felix Bloch Institute for Solid State Physics, University of Leipzig, Linnstrasse 5, 04103 Leipzig, Germany. Electronic address: j.haase@physik.uni-leipzig.de.

PMID: 30953924
DOI: 10.1016/j.jmr.2019.03.008

Abstract

Three-dimensional topological insulators are an important class of modern materials, and a strong spin-orbit coupling is involved in making the bulk electronic states very different from those near the surface. Bi₂Se₃ is a model compound, and ²⁰⁹Bi NMR is employed here to investigate the bulk properties of the material with focus on the quadrupole splitting. It will be shown that this splitting measures the energy band inversion induced by spin-orbit coupling in quantitative agreement with first-principle calculations. Furthermore, this quadrupole interaction is very unusual as it can show essentially no angular dependence, e.g., even at the magic angle the first-order splitting remains. Therefore, it is proposed that the magnetic field direction is involved in setting the quantization axis for the electrons, and that their life time leads to a new electronically driven relaxation mechanism, in particular for quadrupolar nuclei like ²⁰⁹Bi. While a quantitative understanding of these effects cannot be given, the results implicate that NMR can become a powerful tool for the investigation of such systems.

Keywords: Energy band inversion; Quadrupole interaction; Spin-orbit coupling; Topological insulator.