Scaling Behavior of Dielectric Switching in Nano-assemblies

Recently, we have reported a field-induced sign-switch of dielectric constant ($\varepsilon $') for urea-coated Ba$_{0.8}$Rb$_{0.4}$Ti$_{O}$(C$_{2}$O$_{4})_{2}$ nano-particles (U-BRTOCO) in silicone oil and demonstrated that the observed negative $\varepsilon $' is an intrinsic property of the nano-particle assemblies A systematic study has been subsequently carried out on the switching of $\varepsilon $' under a bias field for U-BRTOCO and other nano-particle assemblies under different conditions. The switching frequency ($\omega _{c})$ is found to be closely related to the zero-frequency electrical conductivity ($\sigma $(0)) of the assemblies. Such a scaling behavior for different nano-assemblies under various conditions gives us strong insight of the origin of the negative $\varepsilon $'. The possible models such as plasma and 2D electron-gas (2DEG) are compared.