Collective excitations of a bound-in-the-continuum condensate

Spectra of low-lying elementary excitations are critical to characterize properties of bosonic quantum fluids. Usually these spectra are difficult to observe, due to low occupation of non-condensate states compared to the ground state. Recently, low-threshold Bose-Einstein condensation was realised...

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Bibliographic Details
Published in:Nature communications 2023-06, Vol.14 (1), p.3464-3464, Article 3464
Main Authors: Grudinina, Anna, Efthymiou-Tsironi, Maria, Ardizzone, Vincenzo, Riminucci, Fabrizio, Giorgi, Milena De, Trypogeorgos, Dimitris, Baldwin, Kirk, Pfeiffer, Loren, Ballarini, Dario, Sanvitto, Daniele, Voronova, Nina
Format: Article
Language:English
Subjects:
639/624/399/1022
639/766/119/2791
639/766/119/999
Anisotropy
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Condensates
Electrons
Elementary excitations
Energy
Excitation spectra
Excitons
Humanities and Social Sciences
multidisciplinary
Photoluminescence
Photons
Polaritons
Saddle points
Science
Science (multidisciplinary)
Symmetry
Waveguides
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Summary:Spectra of low-lying elementary excitations are critical to characterize properties of bosonic quantum fluids. Usually these spectra are difficult to observe, due to low occupation of non-condensate states compared to the ground state. Recently, low-threshold Bose-Einstein condensation was realised in a symmetry-protected bound state in the continuum, at a saddle point, thanks to coupling of this electromagnetic resonance to semiconductor excitons. While it has opened the door to long-living polariton condensates, their intrinsic collective properties are still unexplored. Here we unveil the peculiar features of the Bogoliubov spectrum of excitations in this system. Thanks to the dark nature of the bound-in-the-continuum state, collective excitations lying directly above the condensate become observable in enhanced detail. We reveal interesting aspects, such as energy-flat parts of the dispersion characterized by two parallel stripes in photoluminescence pattern, pronounced linearization at non-zero momenta in one of the directions, and a strongly anisotropic velocity of sound. Bound-states-in-the-continuum (BICs) display unique features like symmetry protection from dissipation, long lifetimes and topological charges. Here the authors demonstrate anisotropic Bogoliubov excitation spectrum of polariton condensate from a BIC using a patterned semiconductor GaAs/AlGaAs waveguide.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-023-38939-y