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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 4: Multiferroics (joint session KFM/MA)
KFM 4.1: Vortrag
Montag, 16. März 2020, 15:00–15:20, HSZ 105
Magnetoelectric crystals as model systems of quantum optics — •Janek Wettstein1, Andrei Pimenov1, Alexander A. Mukhin2, Artem Kuzmenko2, Kirill Amelin3, Toomas Rõõm3, Urmas Nagel3, and David Szaller1 — 1Institute of Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria — 2A. M. Prokhorov General Physics Institute, Russian Academy of Sciences, 119991 Moscow, Russia — 3National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
The interaction between an ensemble of non-interacting two-level quantum systems and a bosonic field is theoretically described by the Dicke-model which predicts a quantum phase transition in the thermodynamic limit when the strength of the interaction reaches a sufficiently large critical value [1,2]. Here, based on the idea of Ref. [3] we present a method to study the superradiant phase transition in SmFe3(BO3)4, where isolated rare-earth quasi-spins (Sm) play the role of the two-level system and the bosonic field is provided by the spin-waves (i.e. magnons) of the antiferromagnetically ordered Fe ions. At low temperatures (T=3 K) we observe an avoided crossing of the optically active low-frequency iron magnon and the Sm quasispin excitations with a coupling of about 70% of the critical value needed for the superradiant transition. The strength of the coupling was tuned by varying density and population of the Sm two-level systems.
[1] K. Hepp and E. H. Lieb, Phys. Rev. A 8, 2517 (1973).
[2] Y. K. Wang and F. T. Hioe, Phys. Rev. A 7, 831 (1973).
[3] X. Li et al., Science 361, 794 (2018).