Search for time reversal symmetry breaking in multiband superconductors
Final Report Abstract
This project resulted in 3 important contributions to the field of superconductivity: 1. Within this project, we discovered the first example of an s+is superconductor. We found this novel BTRS superconducting state in the Ba1-xKxFe2As2 system at the narrow doping range using specific heat and μSR measurements supplemented by theoretical analysis. The results of this work were published in Nature Physics. 2. Further studies of the Ba1-xKxFe2As2 system lead to unusual findings of a new state of matter, which exits above the superconducting phase transition and is distinct by symmetry from both superconducting and normal metal phases. Our data shows that this is a bosonic metal state in which Cooper pairs of electrons lack coherence, but the system spontaneously breaks time-reversal symmetry. The theoretical analysis performed in the group of Egor Babaev indicates that the observations are consistent with the theory of a state with fermionic quadrupling, in which long-range order exists not between Cooper pairs but only between pairs of pairs. The results of this work were published in Nature Physics. This article attracted huge online attention, according to the information on Nature Physics. This discovery opens a new research direction. 3. Within this project, we also performed the first muon spin rotation/relaxation (µSR) studies under uniaxial strain on Sr2RuO4, the most famous example of a superconductor with multicomponent chiral order parameter. Using a specially developed uniaxial-strain apparatus, we verified one of the key theoretical predictions of chiral superconductivity - the splitting of the superconducting and the time-reversal symmetrybreaking transitions under uniaxial strain. This study was also published in Nature Physics and highlighted in Physics Today.
Publications
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Superconductivity with broken time-reversal symmetry inside a superconducting s-wave state. Nature Physics, 16(7), 789-794.
Grinenko, V.; Sarkar, R.; Kihou, K.; Lee, C. H.; Morozov, I.; Aswartham, S.; Büchner, B.; Chekhonin, P.; Skrotzki, W.; Nenkov, K.; Hühne, R.; Nielsch, K.; Drechsler, S. -L.; Vadimov, V. L.; Silaev, M. A.; Volkov, P. A.; Eremin, I.; Luetkens, H. & Klauss, H.-H.
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Split superconducting and time-reversal symmetry-breaking transitions in Sr2RuO4 under stress. Nature Physics, 17(6), 748-754.
Grinenko, Vadim; Ghosh, Shreenanda; Sarkar, Rajib; Orain, Jean-Christophe; Nikitin, Artem; Elender, Matthias; Das, Debarchan; Guguchia, Zurab; Brückner, Felix; Barber, Mark E.; Park, Joonbum; Kikugawa, Naoki; Sokolov, Dmitry A.; Bobowski, Jake S.; Miyoshi, Takuto; Maeno, Yoshiteru; Mackenzie, Andrew P.; Luetkens, Hubertus; Hicks, Clifford W. & Klauss, Hans-Henning
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State with spontaneously broken time-reversal symmetry above the superconducting phase transition. Nature Physics, 17(11), 1254-1259.
Grinenko, Vadim; Weston, Daniel; Caglieris, Federico; Wuttke, Christoph; Hess, Christian; Gottschall, Tino; Maccari, Ilaria; Gorbunov, Denis; Zherlitsyn, Sergei; Wosnitza, Jochen; Rydh, Andreas; Kihou, Kunihiro; Lee, Chul-Ho; Sarkar, Rajib; Dengre, Shanu; Garaud, Julien; Charnukha, Aliaksei; Hühne, Ruben; Nielsch, Kornelius ... & Babaev, Egor
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Unsplit superconducting and time reversal symmetry breaking transitions in Sr2RuO4 under hydrostatic pressure and disorder. Nature Communications, 12(1).
Grinenko, Vadim; Das, Debarchan; Gupta, Ritu; Zinkl, Bastian; Kikugawa, Naoki; Maeno, Yoshiteru; Hicks, Clifford W.; Klauss, Hans-Henning; Sigrist, Manfred & Khasanov, Rustem
