Acoustic Driving Enables Controlled Condensation Of Light And Matter On Chip

An international research team led by Alexander Kuznetsov at the Paul Drude Institute for Solid State Electronics (PDI) in Berlin has demonstrated a fundamentally new way to control the condensation of hybrid light-matter particles. Using coherent acoustic driving to dynamically reshape the energy landscape of a semiconductor microcavity, the researchers achieved deterministic steering of a macroscopic quantum state into its lowest energy configuration. The results, published today in Nature Photonics, establish a strategy for engineering nonequilibrium quantum states and open prospects for ultrafast, tunable photonic technologies.

In collaboration with long term partners from the National Scientific and Technical Research Council CONICET and the Bariloche Atomic Centre and Balseiro Institute in Argentina, the team experimentally realized a universal scheme for selectively transferring population within a multilevel quantum system using strong time periodic modulation.

The study focuses on exciton polaritons, quasiparticles that emerge when light confined in a microcavity strongly couples to electronic excitations in a semiconductor. Because they behave as bosons, exciton polaritons can undergo nonequilibrium Bose Einstein condensation, forming a coherent macroscopic quantum state that emits light with laser like properties.

In the experiments, a gigahertz frequency acoustic wave periodically modulated the system’s energy levels, reshaping the condensate landscape and driving the population into the lowest energy state. The resulting emission exhibited a single dominant level with a comb of spectral lines at gigahertz repetition rates and picosecond scale correlations.

The mechanism is described within the framework of coherent Floquet driving. The periodic modulation alters the balance between excitonic and photonic components and enables controlled occupation of quantum states. A theoretical model reproduces the observed dynamics and attributes the population transfer to the interplay between bosonic stimulation and adiabatic Landau-Zener type transitions.

Controlling nonequilibrium quantum systems is a central challenge in condensed matter physics. By demonstrating deterministic steering of a driven many body condensate in a solid state platform, the study establishes semiconductor microcavities as a platform for dynamic quantum engineering and suggests new routes toward tunable, ultrafast coherent light sources relevant for photonics and optoelectronics.