Investigating electromechanical coupling between membrane crystal materials and superconducting microwave resonators
This work studies the use of two-dimensional (2D) crystal materials as mechanical elements in an electromechanical resonant system. 2D materials form crystals that have strong in-plane bonds but weak out-of-plane bonds, allowing for their separation into thin planar layers. Graphene and niobium diselenide are two such materials studied, and they are suspended as electrodes in a parallel plate capacitor. When this capacitor is integrated into an electromagnetic resonant circuit, any movement of this suspended material will greatly effect the resonance frequency of the circuit. Measurement of the resonance frequency allows a dispersive readout of the motion. This system of two coupled harmonic oscillators has the potential to demonstrate strong coupling where the two must be described in a combined state. The light-matter interactions can pave the way to quantum-limited measurement of position and perhaps a means to control, measure, and store qubit information in quantum computing systems. A method to fabricate and optically characterize suspended capacitor devices was developed with the ultimate goal of testing in a dilution refrigerator. Low loss superconducting aluminum integrated circuits were designed and made with these capacitors to allow microwave readout and interaction with the motion of the vibrating membrane materials. Predictions on the microwave electromechanical sideband output shows feasibility for future cryogenic measurements of the 2D crystal motion.