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arXiv · 2010.02110

Topological magnetic order and superconductivity in EuRbFe$_4$As$_4$

M. Hemmida·N. Winterhalter-Stocker·D. Ehlers·H. -A. Krug von Nidda·M. Yao·J. Bannies·E. D. L. Rienks·R. Kurleto·C. Felser·B. Büchner·J. Fink·S. Gorol·T. Förster·S. Arsenijevic·V. Fritsch·P. Gegenwart
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Abstract

We study single crystals of the magnetic superconductor EuRbFe$_4$As$_4$ by magnetization, electron spin resonance (ESR), angle-resolved photoemission spectroscopy (ARPES) and electrical resistance in pulsed magnetic fields up to 630 kOe. The superconducting state below 36.5 K is almost isotropic and only weakly affected by the development of Eu$^{2+}$ magnetic order at 15 K. On the other hand, for the external magnetic field applied along the c-axis the temperature dependence of the ESR linewidth reveals a Berezinskii-Kosterlitz-Thouless topological transition below 15 K. This indicates that Eu$^{2+}$-planes are a good realization of a two-dimensional XY-magnet, which reflects the decoupling of the Eu$^{2+}$ magnetic moments from superconducting FeAs-layers.

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M. Hemmida, N. Winterhalter-Stocker, D. Ehlers, H. -A. Krug von Nidda, M. Yao, J. Bannies, E. D. L. Rienks, R. Kurleto, C. Felser, B. Büchner, J. Fink, S. Gorol, T. Förster, S. Arsenijevic, V. Fritsch, P. Gegenwart. 2020-10-05. Topological magnetic order and superconductivity in EuRbFe$_4$As$_4$. https://doi.org/10.1103/physrevb.103.195112

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