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TT: Fachverband Tiefe Temperaturen

TT 53: Poster Session: Superconductivity 1

TT 53.19: Poster

Mittwoch, 22. März 2017, 15:00–19:00, P2-OG2

Disorder-promoted C₄-symmetric magnetic order in iron-based superconductors — •Mareike Hoyer¹, Rafael M. Fernandes², Alex Levchenko³, and Jörg Schmalian¹ — ¹Institut für Theorie der Kondensierten Materie und Institut für Festkörperphysik, Karlsruher Institut für Technologie, Deutschland — ²School of Physics and Astronomy, University of Minnesota, USA — ³Department of Physics, University of Wisconsin-Madison, USA

In most iron-based superconductors, the transition to the magnetically ordered state is closely linked to a lowering of structural symmetry from tetragonal (C₄) to orthorhombic (C₂). However, recently, a regime of C₄-symmetric magnetic order has been reported in certain hole-doped compounds. This novel magnetic ground state can be understood as a double-Q spin density wave, and depending on the relative orientations of the two order parameters M₁ and M₂, either a noncollinear spin-vortex crystal (SVC) or a nonuniform charge-spin density wave (CSDW) could form. Experimentally, CSDW has been established as the magnetic configuration of some of these optimally hole-doped compounds, whereas in low-energy itinerant models SVC and CSDW states are nearly degenerate. Extensions of these low-energy models including additional electronic interactions even tip the balance in favor of the SVC, in apparent contradiction with the recent experimental findings.

Here, we revisit the phase diagram of magnetic ground states of low-energy multi-band models in the presence of weak disorder. We show that impurity scattering not only promotes the transition from C₂ to C₄-magnetic order, but also favors the CSDW over the SVC phase.