New experimental platform for two-dimensional helium film adsorbed on a graphene substrate

Graphite substrate has been widely utilized to investigate the exotic properties in two-dimensional adsorbed films. Especially, adsorbed ⁴He film on graphite exhibits various interesting nonclassical phases such as a registered solid phase and a superfluid phase. However, the intriguing quantum behaviors have not been clarified due to the lack of sensitivity by the unwanted tortuosity in conventional graphite substrates. Here, we propose a cavity optomechanical system as a new experimental platform to resolve the properties of the helium on graphite. The mass and stiffness change on the helium film can be directly reflected on responses of the graphene mechanical resonator. The mechanical motion of a graphene resonator can be monitored through a capicively coupled superconducting coplanar waveguide cavity using optomechanically induced transparency. We present the progress in the fabrication of the on-chip cavity optomechanical system. This highly sensitive measurement scheme can be utilized as an ultimate platform to study the 2D nature of quantum and classical gases.