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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 17: Microstructure, Real Structure and Crystal Defects
KFM 17.4: Vortrag
Freitag, 20. März 2020, 10:30–10:50, TOE 317
Exploring electronic properties of topological insulators using nuclear magnetic resonance — •Robin Guehne and Jürgen Haase — Felix Bloch Institute, Leipzig University, Leipzig, Germany
The investigations of 3-dimensional topological insulators such as Bi2Se3 focus chiefly on the gapless surface states that emerge as a consequence of the special energy band inversion near the Fermi level induced by spin-orbit coupling. Not as much studied are the real-space properties of the bulk, although, the band inversion, for example, changes the wave function of the free carriers in the bulk, compared to the topologically trivial counterpart without band inversion.
Recently we have shown that nuclear magnetic resonance (NMR) as a local, bulk probe can detect this band inversion through the electric quadrupole interaction that, in addition, measures the concentration of free carriers, e.g. originating from self-doping effects [1]. Furthermore, our orientation dependent 209Bi NMR experiments in single crystalline Bi2Se3 reveal a so far unknown effect in condensed matter – a magnetic field induced charge symmetry that leaves the electric field gradient at the Bi site to rotate rather freely with the external magnetic field B0 due to spin-orbit coupling as experienced by conduction electrons.
NMR data in external fields up to 17 T, i.e., shifts, linewidths and quadrupole splittings, in three-dimensional topological insulators will be discussed.
[1] R. Guehne, V. Chlan, G. V.M. Williams, S. V. Chong, K. Kadowaki, A. Pöppl, and J. Haase. J. Magn. Res. 302, 34 - 42 (2019)