Mechanical oscillators for the detection of casimir force between superconductors

Abstract

The Casimir force is an attractive force between reflective surfaces predicted in the 1948 and measured very accurately in the 2000s. These measurements are in good agreement with the plasma model for the permittivities of conductors while it is generally admitted that the Drude model is a more accurate description. Differences between the models are non-negligible only at low frequencies so it has been proposed to measure the force through a superconducting transition since only the low frequencies' contribution to the force changes through this transition. This would enable to monitor the behavior of those low frequency components separately. In the thesis, I explain and calculate the numerical estimates for the Casimir force between both normal and superconducting aluminium plates and show how a cavity optomechanical device involving a superconducting drum membrane oscillator can be used to measure such a force. Based on the estimates, I present a design of a superconducting on-chip cavity with integrated mechanics. The numerical estimates are very favorable and show that the platform is well suited for Casimir force measurements. I also detail the fabrication process that I carried out and improved throughout the project to implement this design. While fabrication-related issues prevented me from finalizing these samples, I was able to identify these problems and likely solutions to be implemented in the future fabrication rounds. The project also allowed to start building the experimental system that will eventually allow to carry out this Casimir force measurement project.