Parametric Instabilities of Interacting Bosons in Periodically Driven 1D Optical Lattices

New states of matter can arise when a system is exposed to a periodic drive, such as by irradiating a solid with light or by mechanically shaking a gas of ultracold atoms. While experiments have validated this method, the target often exhibits a drastically reduced lifetime because it continuously absorbs energy from the drive. Moreover, in systems of bosonic particles the periodic drive can trigger the rapid growth of collective excitations, known as parametric instabilities, which typically decay and result in additional heating.

Here, we report on observations of collective modes in the early-stage dynamics of ultracold bosons in shaken one-dimensional optical lattices by monitoring the momentum distribution of the cloud. Our observations confirm recent theoretical predictions and directly show the important role played by parametric instabilities during early evolution times for a wide class of shaken quantum systems with bosonic elementary excitations.

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