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TT: Fachverband Tiefe Temperaturen

TT 52: Superconductivity: Fe-based Superconductors – FeSe and others

TT 52.6: Talk

Wednesday, March 18, 2015, 10:45–11:00, H 2053

Correlation-driven topological Fermi surface transition in FeSeI. Leonov1, •S. L. Skornyakov2,3, V. I. Anisimov2,3, and D. Vollhardt11TP III, Center for Electronic Correlations and Magnetism, Univ. Augsburg, Germany — 2Institute of Metal Physics, Yekaterinburg, Russia — 3Ural Federal Univ., Yekaterinburg, Russia

We present results of a theoretical investigation of the electronic structure and phase stability of paramagnetic FeSe obtained within a combination of ab initio methods for calculating band structure and dynamical mean-field theory [1]. Our results reveal an entire reconstruction of the Fermi surface topology upon a moderate expansion of the lattice (Lifshitz transition), with a change of magnetic correlations from the in-plane magnetic wave vector (π,π) to (π,0). We attribute this behavior to a correlation-induced shift of the Van Hove singularity originating from the dxy and dxz/dyz bands at the M-point across the Fermi level. Our results predict a structural transition of FeSe upon a ca. 10% expansion of the lattice volume as well as a topological change of the Fermi surface of FeSe upon partial substitution Se by Te, which is accompanied with a sharp increase of the local moments. We expect that these changes are responsible for the experimentally observed increase of Tc in FeSe upon doping with Te. The microscopic origin for superconductivity in this system is then due to a Van Hove singularity close to the Fermi level. This identification may open a new route to increase Tc even further.


[1] I. Leonov, S. L. Skornyakov, V. I. Anisimov, D. Vollhardt,

arXiv:1411.0604 (2014).

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