  Observations suggest that protoplanetary disks have moderate accretion rates
onto the central young star, especially at early stages (e.g. HL Tau),
indicating moderate disk turbulence. However, recent ALMA observations suggest
that dust is highly settled, implying weak turbulence. Motivated by such
tension, we carry out 3D stratified local simulations of self-gravitating
disks, focusing on settling of dust particles in actively accreting disks. We
find that gravitationally unstable disks can have moderately high accretion
rates while maintaining a relatively thin dust disk for two reasons. First,
accretion stress from the self-gravitating spirals (self-gravity stress) can be
stronger than the stress from turbulence (Reynolds stress) by a factor of 5-20.
Second, the strong gravity from the gas to the dust decreases the dust scale
height by another factor of $\sim 2$. Furthermore, the turbulence is slightly
anisotropic, producing a larger Reynolds stress than the vertical dust
diffusion coefficient. Thus, gravitoturbulent disks have unusually high
vertical Schmidt numbers ($Sc_z$) if we scale the total accretion stress with
the vertical diffusion coefficient (e.g. $Sc_z\sim$ 10-100). The reduction of
the dust scale height by the gas gravity, should also operate in
gravitationally stable disks ($Q>$1). Gravitational forces between particles
become more relevant for the concentration of intermediate dust sizes, forming
dense clouds of dust. After comparing with HL Tau observations, our results
suggest that self-gravity and gravity among different disk components could be
crucial for solving the conflict between the protoplanetary disk accretion and
dust settling, at least at the early stages.
