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[Stage/Thèse] Fermionic and bosonic limit of collective electronic excitations

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Stage de Master 2 qui débouche sur une thèse :

Fermionic and bosonic limit of collective electronic excitations

Person in charge of the internship : Angela Vasanelli
Tel : 0157276226
e-mail : angela.vasanelli@univ-paris-diderot.fr

Scientific project :
Ultra-strong light-matter coupling is a regime of quantum electrodynamics reached when the light–matter coupling energy is of the same order of magnitude as that of the matter excitation or of the cavity photon [1]. In this regime, polarization self-interaction and counter-rotating terms, usually neglected, have to be included in the Hamiltonian describing the system. This has strong consequences on the physics of the resulting quasi-particles and fascinating effects are expected to appear, like dynamical Casimir effect, superradiant phase transitions, photon blockade, extraordinary conductance.
In our group we pioneered an experimental platform for the observation of ultra-strong coupling regime, based on two-dimensional (2D) plasmons, which are collective electronic excitations confined in a semiconductor quantum well (see figure) [2].

two-dimensional (2D) plasmons
two-dimensional (2D) plasmons

When they are coupled with free-space photons, 2D plasmons superriadiantly decay with a lifetime orders of magnitude shorter than that of a single particle at the same wavelength [3]. When 2D plasmons are inserted in a metallic resonator, the ultra-strong coupling regime is observed, with record values of the relative coupling energy [4,5].
The aim of this project is to explore the fermionic and the bosonic limit of these collective electronic excitations. In the low excitation limit, 2D plasmons behave as composite bosons. In this regime we will study stimulated scattering phenomena under optical pumping, with the ultimate goal of accumulating such bosons in a single ground state and achieving a coherent condensate. For the fermionic limit, we will study few-electron systems obtained by using metamaterial resonators, in which 2D plasmons are ultra-strongly coupled with the resonator mode [6]. This regime will be explored under optical pumping, for the observation of photon blockade effect, and under electrical pumping, in order to investigate how the electronic transport can be modified by the ultra-strong coupling with a photonic mode.
[1] C. Ciuti, G. Bastard and I. Carusotto, Phys. Rev. B 72, 115303 (2005).
[2] A. Delteil et al. Phys. Rev. Lett. 109, 246808 (2012).
[3] T. Laurent,et al. Phys. Rev. Lett. 115, 187402 (2015).
[4] Y. Todorov, et al. Phys. Rev. Lett. 105, 196402 (2010).
[5] B. Askenazi et al. ACS Photonics (2017)
[6] Y. Todorov and C. Sirtori, Phys. Rev. X 4, 041031 (2014)

Methods and techniques : Mid and far infrared spectroscopy, transport measurements
Possibility to go on with a PhD ? Yes
Envisaged fellowship ? ED, Quantera project submitted

Fermionic and bosonic limit of collective electronic excitations