Tunable Casimir equilibria with phase change materials: From quantum trapping to its release

Abstract

A stable suspension of nanoscale particles due to the Casimir force is of great interest for many applications such as sensing, noncontract nanomachines. However, the suspension properties are difficult to change once the devices are fabricated. Vanadium dioxide (${\mathrm{VO}}_{2}$) is a phase change material, which undergoes a transition from a low-temperature insulating phase to a high-temperature metallic phase around a temperature of 340 K. In this work, we study Casimir forces between a nanoplate (gold or Teflon) and a layered structure containing a ${\mathrm{VO}}_{2}$ film. It is found that stable Casimir suspensions of nanoplates can be realized in a liquid environment, and the equilibrium distances are determined, not only by the layer thicknesses but also by the matter phases of ${\mathrm{VO}}_{2}$. Under proper designs, a switch from quantum trapping of the gold nanoplate (``on'' state) to its release (``off'' state) as a result of the metal-to-insulator transition of ${VO}_{2}$, is revealed. On the other hand, the quantum trapping and release of a Teflon nanoplate is found under the insulator-to-metal transition of ${\mathrm{VO}}_{2}$ . Our findings offer the possibility of designing switchable devices for applications in micro and nanoelectromechanical systems.