Regensburg 2022 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 18: Topological Insulators
TT 18.4: Vortrag
Mittwoch, 7. September 2022, 10:15–10:30, H23
Chern insulating phases and thermoelectric properties of EuO/MgO(001) superlattices — •Okan Koeksal and Rossitza Pentcheva — Department of Physics and Center of Nanointegration (CENIDE), University of Duisburg-Essen, 47057 Duisburg
The effect of confinement and strain on the topological and thermoelectric properties of (EuO)n/(MgO)m(001) superlattices (SLs) are investigated by means of DFT + U + spin-orbit coupling (SOC) calculations in conjunction with semi-classical Boltzmann transport theory. A particularly strong effect is observed in the ferromagnetic (EuO)1/(MgO)3(001) SL at the lateral lattice constant of MgO (a = 4.24 Å) where SOC opens a band gap of 0.51 eV due to an inversion between occupied localized Eu 4f and itinerant 5d conduction bands. This band inversion between bands of opposite parity is accompanied by a spin reorientation in the spin-texture along the contour of band surrounding the Γ point. The resulting Chern insulating phase with C = –1, confirmed by a single topological edge state, exhibits promising thermoelectric properties, i.e., a high Seebeck coefficient between 400 and 800 µVK−1. Somewhat lower thermoelectric values are obtained for the ferromagnetic semimetallic (EuO)2/(MgO)2(001) SL, where SOC also induces a band inversion and AHC with values up to –1.04 e2/h. This work emphasizes the correlation between non-trivial topology and thermoelectricity in (EuO)n/(MgO)m(001) SLs with broken time-reversal symmetry [1].
Support by the DFG within CRC/TRR80, project G3 is gratefully acknowledged.
[1] O. Köksal and R. Pentcheva, Phys. Rev. B 103, 045135 (2021)