Ground state exciton-polariton condensation by coherent Floquet driving

TL;DR

This paper demonstrates a method to control exciton-polariton Bose-Einstein condensates using a GHz acoustic wave, enabling selective population transfer to generate tunable ultrafast laser-like emission.

Contribution

It introduces a universal strategy for Floquet engineering of BECs with acoustic modulation, achieving controlled population transfer and spectral comb generation.

Findings

Successful experimental control of BEC modes with acoustic waves

Generation of GHz repetition rate frequency combs

Theoretical model explaining population dynamics

Abstract

The on-demand selective population transfer between states in multilevel quantum systems is a challenging problem with implications for a wide-range of physical platforms including photon and exciton-polariton Bose- Einstein condensates (BECs). Here, we introduce an universal strategy for this selective transfer based on a strong time-periodic energy modulation, which is experimentally demonstrated by using a GHz acoustic wave to control the gain and loss of confined modes of an exciton-polariton BEC in a microcavity. The harmonic acoustic field shifts the energy of the excitonic BEC component relative to the photonic ones, which generates a dynamic population transfer within a multimode BEC that can be controlled by the acoustic amplitude. In this way, the full BEC population can be selectively transferred to the ground state to yield a single-level emission consisting of a spectral frequency comb with GHz repetition rates as well as picosecond-scale correlations. A theoretical model reproduces the observed time evolution and reveals a dynamical interplay between bosonic stimulation and the adiabatic Landau-Zener-like population transfer. Our approach provides a new avenue for the Floquet engineering of light-matter systems and enables tunable single- or multi-wavelength ultrafast pulsed laser-like emission for novel information technologies.