  Van der Waals trap, a quantum fluctuation-induced potential characterized by
short-range repulsive and long-range attractive forces, is intrinsically
nonlinear. This work unveils the nonlinear effects on Brownian oscillators in
the van der Waals trap using Langevin dynamics simulations and quasiharmonic
approximations. While neither size- nor temperature-dependences of effective
natural frequency is important for suspended plates of large areas, smaller
ones with broader probability distributions are significantly softened and even
a temperature-induced softening is observed. Despite the nonlinearity, the
stiffness and the coefficient of friction are tunable by changing the thickness
of coating and by modifying the size and the perforation condition of suspended
plates, respectively, endowing the quantum trap with flexibilities of building
up microscopic mechanical systems and probing near-boundary hydrodynamics.
