Prof. Alejandro Fainstein

Centro Atómico Bariloche and Instituto Balseiro (CNEA), 8400 Bariloche, Argentina.

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Lattices of exciton polariton condensates represent a rich platform for the study and implementation of non-Hermitian non-linear bosonic quantum systems. Actuation with a time dependent drive provides the means, for example, to perform Floquet engineering, Landau-Zenner-Stückelberg state preparation, and to induce resonant inter-level transitions. With this perspective we introduce polaromechanical metamaterials, two-dimensional arrays of m-size zero-dimensional traps confining light-matter polariton fluids and GHz phonons. 
A strong exciton-mediated polariton-phonon interaction [1] can be exploited in these metamaterials, both using electrically injected bulk-acoustic waves [2] or self-induced coherent mechanical oscillations [3], to induce a time-dependence in the level energies and/or in the inter-site polariton coupling J(t). This has remarkable consequences for the dynamics. For example, when locally perturbed by continuous wave optical excitation, polariton condensates respond by locking the energy detuning between neighbor sites at multiples of the phonon energy [4]. We theoretically describe these observations in terms of synchronization phenomena involving the polariton and phonon fields. We study lattices of closely connected traps (defined by a linear optomechanical coupling), and also well separated traps (characterized by a quadratic optomechanical coupling), and discuss the role of dissipation and non-linearities in the stability of the observed asynchronous locking. The described metamaterials open the path for the study of non-reciprocal transport in dissipative quantum light fluids spatially and temporally modulated by GHz hypersound. 

[1] P. Sesin et al., Giant optomechanical coupling and dephasing protection with cavity exciton-polaritons, arXiv:2212.08269.
[2] A. S. Kuznetsov et al., Electrically Driven Microcavity Exciton-Polariton Optomechanics at 20 GHz, Physical Review X 11, 021020 (2021).
[3] D. L. Chafatinos et al., Polariton-Driven Phonon Laser, Nature Communications 11, 4552 (2020).
[4] R D. L. Chafatinos et al., Asynchronous Locking in Metamaterials of Fluids of Light and Sound, arXiv:2112.00458, Nature Communications (in press).