Electromagnetic fluctuation-induced interactions, such as Casimir and van der Waals forces due to dipolar fluctuations, are ubiquitous in nature. These interactions are particularly prominent at microscales and nanoscales, and they are critically important for the stability of various types of composites. Similar to dipolar fluctuations, ionic charge-density fluctuations, which determine the behavior of ionic solutions, can mediate an attractive dispersive force between bounding surfaces. We show that a new fluctuation mechanism hinging on monopolar charge fluctuations of objects can be quite important, and it can result in a dispersive interaction similar to Casimir and van der Waals forces.
We consider a parallel-plate capacitor made of a graphene nanostructure and a metallic substrate. Charge fluctuations, transferred on the capacitor by a connecting wire, induce a dispersive attractive force between the plates, which becomes especially prominent in nanostructures. Our novel theory utilizes the quantum capacitance concept, and it distinguishes between thermal and quantum mechanical contributions. We demonstrate that the charge-induced fluctuation force exists in conjunction with the more commonly studied Casimir force and that it can even become stronger than the Casimir force.
Our results are strong evidence that there are different types of dispersive interactions, which can enable additional studies of the properties of materials at the microscale and nanoscale.
