Unique interplay between superconducting and ferromagnetic orders in EuRbFe$_4$As$_4$

V. S. Stolyarov; A. Casano; M. A. Belyanchikov; A. S. Astrakhantseva; S. Yu. Grebenchuk; D. S. Baranov; I. A. Golovchanskiy; I. Voloshenko; E. S. Zhukova; B. P. Gorshunov; A. V. Muratov; V. V. Dremov; L. Ya. Vinnikov; D. Roditchev; Y. Liu; G. -H. Cao; M. Dressel; E. Uykur

doi:10.1103/physrevb.98.140506

arXiv · 1807.04135

Unique interplay between superconducting and ferromagnetic orders in EuRbFe$_4$As$_4$

V. S. Stolyarov·A. Casano·M. A. Belyanchikov·A. S. Astrakhantseva·S. Yu. Grebenchuk·D. S. Baranov·I. A. Golovchanskiy·I. Voloshenko·E. S. Zhukova·B. P. Gorshunov·A. V. Muratov·V. V. Dremov·L. Ya. Vinnikov·D. Roditchev·Y. Liu·G. -H. Cao·M. Dressel·E. Uykur

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Abstract

Transport, magnetic and optical investigations on EuRbFe$_4$As$_4$ single crystals evidence that the ferromagnetic ordering of the Eu$^{2+}$ magnetic moments at $T_N=15$ K, below the superconducting transition ($T_c=36$ K), affects superconductivity in a weak but intriguing way. Upon cooling below $T_N$, the zero resistance state is preserved and the superconductivity is affected by the in-plane ferromagnetism mainly at domain boundaries; a perfect diamagnetism is recovered at low temperatures. The infrared conductivity is strongly suppressed in the far-infrared region below $T_c$, associated with the opening of a complete superconducting gap at $2\Delta = 10$ meV. A gap smaller than the weak coupling limit suggests the strong orbital effects or, within a multiband superconductivity scenario, the existence of a larger yet unrevealed gap.

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V. S. Stolyarov, A. Casano, M. A. Belyanchikov, A. S. Astrakhantseva, S. Yu. Grebenchuk, D. S. Baranov, I. A. Golovchanskiy, I. Voloshenko, E. S. Zhukova, B. P. Gorshunov, A. V. Muratov, V. V. Dremov, L. Ya. Vinnikov, D. Roditchev, Y. Liu, G. -H. Cao, M. Dressel, E. Uykur. 2018-07-11. Unique interplay between superconducting and ferromagnetic orders in EuRbFe$_4$As$_4$. https://doi.org/10.1103/physrevb.98.140506

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