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DS: Fachverband Dünne Schichten
DS 15: Thermoelectric Materials
DS 15.6: Talk
Tuesday, March 8, 2016, 11:15–11:30, H8
Electronic topological transition in epitaxially strained delafossite PtCoO2 — •Markus E. Gruner1,2, Ulrich Eckern3, and Rossitza Pentcheva2,1 — 1Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II), Technical University Munich — 2Faculty of Physics and Center for Nanointegration, CENIDE, University of Duisburg-Essen — 3Institute of Physics, University of Augsburg
The hexagonal delafossites PdCoO2 and PtCoO2 exhibit highly anisotropic transport properties including large negative values of the thermopower Szz perpendicular to the hexagonal plane [1], which is of interest for thermoelectric energy conversion or sensor applications.
By means of DFT calculations combined with semiempirical
Boltzmann transport theory in the single relaxation time approximation we explore the effect of strain on the thermoelectric properties of both systems.
We demonstrate that, despite their rather similar structural response, the isoelectronic compounds differ significantly in their transport behavior under tensile and compressive expitaxial strain [2].
This is related to specific changes of the Fermi surface
involving an electronic topological transition, which occurs
in PtCoO2 at moderate compressive strain.
Combining our first-principles results with available experimental data, we estimate a maximum ZT of 0.25 obtained for PtCoO2 under −4 % epitaxial strain.
Funding by the DFG (TRR80) is gratefully acknowledged.
[1] K.P. Ong, D.J. Singh, P. Wu, Phys. Rev. Lett. 104, 176601 (2014)
[2] M.E. Gruner, U. Eckern, R. Pentcheva, arXiv:1511.09087