Ga(Al)As microcavities provide a platform for studying strong exciton-photon coupling and interactions with GHz cavity phonons. This leads to exciton-polaritons—quasi-particles combining the low mass of photons with excitonic nonlinearity. Polaritons in these structures also couple efficiently to confined phonons (7–100 GHz) and can form Bose-Einstein condensates with a well-defined pseudospin under non-resonant excitation.
Non-resonant excitation can induce a self-sustained pseudospin precession, breaking continuous time translation symmetry and forming a continuous time crystal (CTC). When coupled to the cavity’s mechanical mode, the CTC oscillations exert an optical force, and increasing excitation power enhances polariton nonlinearities, shifting the precession frequency toward that of the mechanical mode. This can trigger self-oscillation of the mechanical vibrations, leading to frequency locking of the CTC to the phonon frequency.
Here, we extend the study of the CTC phase by introducing a resonant excitation alongside the non-resonant laser. We demonstrate coherent control of the pseudospin dynamics through frequency pulling and injection locking, enabling tunability of the precession frequency or its suppression. These mechanisms offer new pathways for resonant mechanical excitation, CTC control, and inter-site coupling in polariton condensate arrays, with potential applications in non-reciprocal transport.