Experimental verification of the very strong coupling regime in a GaAs quantum well microcavity
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The dipole coupling strength g between cavity photons and quantum well excitons determines the regime of light matter coupling in quantum well-microcavities. In the strong coupling regime, a reversible energy between exciton and cavity photon takes place, which leads to the formation of hybrid polaritonic resonances. If the coupling is further increased, a hybridization of different single exciton states emerges, which is referred to as the very strong coupling regime. In semiconductor quantum wells such a regime is predicted to manifest as a photon-mediated electron-hole coupling leading to different excitonic wave functions for the two polaritonic branches when the ratio of the coupling strength to exciton binding energy gEB/ approaches unity. Here, we verify experimentally the existence of this regime in magneto-optical measurements on a microcavity characterized by gEB/≈0.64, showing that the average electron-hole separation of the upper polariton is significantly increased compared to the bare quantum well exciton Bohr radius. This yields a diamagnetic shift around zero detuning that exceeds the shift of the lower polariton by one order of magnitude and the bare quantum well exciton diamagnetic shift by a factor of two. The lower polariton exhibits a diamagnetic shift smaller than expected from the coupling of a rigid exciton to the cavity mode which suggests more tightly bound electron-hole pairs than in the bare quantum well.
Brodbeck , S , De Liberato , S , Amthor , M , Klaas , M , Kamp , M , Worschech , L , Schneider , C & Höfling , S 2017 , ' Experimental verification of the very strong coupling regime in a GaAs quantum well microcavity ' Physical Review Letters , vol. 119 , no. 2 , 027401 . https://doi.org/10.1103/PhysRevLett.119.027401
Physical Review Letters
© 2017, American Physical Society. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at journals.aps.org / https://doi.org/10.1103/PhysRevLett.119.027401
DescriptionThis work was supported by the State of Bavaria. S.D.L. acknowledges support from a Royal Society Research Fellowship and from EPSRC Grant No. EP/M003183/1.
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