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TT: Fachverband Tiefe Temperaturen

TT 35: Superconductivity: Fe-based Superconductors - 122 and Theory

TT 35.5: Vortrag

Dienstag, 13. März 2018, 10:30–10:45, A 053

Mass enhancements and band shifts in hole overdoped Fe-based pnictide superconductors: KFe₂As₂ and CsFe₂As₂ — •S.-L. Drechsler¹, H. Rosner², V. Grinenko³, S. Aswartham¹, I. Morozov⁴, L. Ming⁴, A. Boltalin⁴, K. Kihou⁵, C. H. Lee⁵, T. K. Kim⁶, D. Evtushinsky⁷, J.M. Tomczak⁸, S. Johnston⁹, and S. Borisenko¹ — ¹IFW-Dresden, Germany — ²MPI-CPfS Dresden, Germany — ³TU Dresden, Germany — ⁴Moscow University, Russia — ⁵AIST, Tsuk. Japan — ⁶Diamond Light Source, U.K. — ⁷Ec. de Fed., Lausanne, Switzerland — ⁸Vienna-University of Technology, Austria — ⁹Tennesee University, Knoxville, USA

The interplay of high- and low energy (LE) mass renormalizations with band shifts as seen in the positions of van Hove singularities (VHS) in the normal state of the strongly correlated and most hole-overdoped AFe₂As₂ (A122), A = K,Rb,Cs Fe pnictides is discussed phenomenologically from ARPES data and band structure (GGA) with full spin-orbit coupling and microscopically applying the GW-self-energy. The increase of the Sommerfeld coefficient γ from K122 to Cs122 is ascribed to an enhanced coupling to LE bosons in the vicinity of a quantum critical point to an yet unknown incommensurate phase different from the tetragonal Mott phase. We find no sizable increase of correlation for Cs122 in contrast to scenarios proposed in the literature. The ARPES positions of VHS as compared with GGA and GW results point to slightly weaker correlations in accord with the low-T susceptibility data and the reduced Wilson ratio χ(0)/γ. Other quasi-2D systems with generic VHS and their el-el interactions are briefly discussed.