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Control of Elementary Excitations by Acoustic Fields

Solid state systems host a plethora of useful crystal excitations, e.g., electrons, holes, excitons, polaritons and magnons, to name a few. Future electronic and optoelectronic (quantum) devices will critically depend on the precise control (i.e., transport, tuning of the energy spectrum, etc.) of the aforementioned material excitations. The latter are very sensitive to the changes of the relative positions of atoms in the crystal lattice (i.e. the strain). Phonons, which are quanta of lattice vibrational modes, have been recognized as a useful source of dynamic strain.

This motivates us to explore control-by-strain at the nanoscale, where we exploit the phononic degrees of freedom by coupling elastic vibrations to a variety of micro- and nanostructures. To this end, we use PDI’s portfolio of high-quality materials (see CReA Nanofabrication) and advanced clean-room techniques to fabricate (nano)structures, which efficiently couple the dynamic strain of surface (SAW) and bulk (BAW) acoustic waves to engineered material excitations. We use efficient piezoelectric transducers that, when excited by high-frequency voltages, generate SAWs and BAWs with frequencies up to 20 GHz.

Our research covers a wide scope ranging from applications in high-frequency telecommunications to quantum information technologies. Several examples are the acoustic modulation of exciton-polaritons and quantum dots in semiconductor microcavities, the manipulation of spins in color centers and flying qubits, as well as magneto-acoustic control in ferromagnetic nanostructures. Furthermore, we investigate interaction regimes, where a single quantum excitation can potentially back-act on the phonon, which holds a great potential for the coherent transduction of quantum information between microwave and optical frequency domains. The complex landscape of physical phenomena in such hybrid acousto-opto-electronic systems and the promising prospects for novel applications inspire the research topics listed below.