Complex oxide acousto-electronics

Surface acoustic waves (SAWs) offer a unique degree of freedom to manipulate charge carriers in a 2 dimensional electron system (2DES). The local lattice deformation couples to electrons (and/or holes) via the piezoelectric or deformation potential, providing a tunable and moveable potential well to trap and shuttle charge carriers on demand. This thesis demonstrates the feasibility of this approach to complex-oxide systems, which offer a wealth of physical phenomena such as correlated insulator states, superconductivity, and magnetism. The field of “Quantum Acoustics” is considered as one of the most promising hybrid quantum technologies for future quantum information processing. Here, a first important step towards implementing quantum acoustics in complex-oxide systems is described, by demonstrating robust acoustoelectric currents/voltages in a LaAlO3/SrTiO3 (LAO/STO) 2DES resulting from electromechanical coupling of SAWs, generated in STO to the 2DES. With the unique combination of properties of the LAO/STO 2DES, which is hard to find in other material systems, our work contributes to building up the fundamentals of “Complex oxide Acousto-electronics”. In addition, it is important to note that many intriguing properties of LAO/STO 2DES emerge when it is exposed to various external stimuli, e.g. very large electric field, magnetic field, extremely low temperature or photon illumination. In this respect, modulating the band structure and the crystal properties by in-situ nanoscale mechanical oscillations, e.g. monochromatic SAW phonon modes, offers a completely new degree of freedom to tune the local properties of complex-oxide interfaces. It may lead to the emergence of novel interesting features and provide new insights into the physics of the LAO/STO 2DES.