Superconductivity with broken time reversal symmetry in ion irradiated Ba$_{0.27}$K$_{0.73}$Fe$_2$As$_2$ single crystals

V. Grinenko; P. Materne; R. Sarkar; H. Luetkens; K. Kihou; C. H. Lee; S. Akhmadaliev; D. V. Efremov; S. -L. Drechsler; H. -H. Klauss

doi:10.1103/physrevb.95.214511

arXiv · 1705.00656

Superconductivity with broken time reversal symmetry in ion irradiated Ba$_{0.27}$K$_{0.73}$Fe$_2$As$_2$ single crystals

V. Grinenko·P. Materne·R. Sarkar·H. Luetkens·K. Kihou·C. H. Lee·S. Akhmadaliev·D. V. Efremov·S. -L. Drechsler·H. -H. Klauss

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Abstract

Over the last years a lot of theoretical and experimental efforts have been made to find states with broken time reversal symmetry (BTRS) in multi-band superconductors. In particular, it was theoretically proposed that in the Ba$_{1-x}$K$_{x}$Fe$_2$As$_2$ system either an $s+is$ or an $s+id$ BTRS state may exist at high doping levels in a narrow region of the phase diagram. Here we report the observation of an enhanced zero field muon spin relaxation rate below the superconducting transition temperature for a high quality crystalline sample with $x \approx$ 0.73. This indicates that indeed the time reversal symmetry is broken in superconducting Ba$_{1-x}$K$_{x}$Fe$_2$As$_2$ at this doping level.

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V. Grinenko, P. Materne, R. Sarkar, H. Luetkens, K. Kihou, C. H. Lee, S. Akhmadaliev, D. V. Efremov, S. -L. Drechsler, H. -H. Klauss. 2017-05-01. Superconductivity with broken time reversal symmetry in ion irradiated Ba$_{0.27}$K$_{0.73}$Fe$_2$As$_2$ single crystals. https://doi.org/10.1103/physrevb.95.214511

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