Shapiro resonances in ac-self-modulated exciton-polariton Josephson junctions

We experimentally investigate the dynamics of exciton polariton Josephson junctions when the coupling between condensates is periodically modulated through self-induced mechanical oscillations. The condensates energy detuning, the analog of the bias voltage in superconducting junctions, displays a plateau behavior akin to the Shapiro steps. At each step massive tunneling of particles occurs featuring Shapiro-like spikes. These characteristic changes are observed when the condensates Josephson frequency ${\omega }_{\text{J}}$ is an integer multiple of the modulation frequency ${\omega }_{\mathrm{M}}$.