  Exact quantum master equation for a driven Brownian oscillator system is
constructed via a Wigner phase-space Gaussian wave packet approach. The
interplay between external field and dissipation leads to this system an
effective field correction that enhances the polarization. This cooperative
property is resulted from an effective bath response to the external field
applied on the system. It is important in the low-frequency driving and
intermediate bath memory region. We demonstrate this non-Markovian effect on
the linear response and nonlinear dynamics and analyze the results together
with analytical asymptotic expressions.
