  The mechanism of angular momentum transport in protoplanetary disks is
fundamental to understand the distributions of gas and dust in the disks. The
unprecedented, high spatial resolution ALMA observations taken toward HL Tau
and subsequent radiative transfer modeling reveal that a high degree of dust
settling is currently achieved at the outer part of the HL Tau disk. Previous
observations however suggest a high disk accretion rate onto the central star.
This configuration is not necessarily intuitive in the framework of the
conventional viscous disk model, since efficient accretion generally requires a
high level of turbulence, which can suppress dust settling considerably. We
develop a simplified, semi-analytical disk model to examine under what
condition these two properties can be realized in a single model. Recent,
non-ideal MHD simulations are utilized to realistically model the angular
momentum transport both radially via MHD turbulence and vertically via
magnetically induced disk winds. We find that the HL Tau disk configuration can
be reproduced well when disk winds are properly taken into account. While the
resulting disk properties are likely consistent with other observational
results, such an ideal situation can be established only if the plasma $\beta$
at the disk midplane is $\beta_0 \simeq 2 \times 10^4$ under the assumption of
steady accretion. Equivalently, the vertical magnetic flux at 100 au is about
0.2 mG. More detailed modeling is needed to fully identify the origin of the
disk accretion and quantitatively examine plausible mechanisms behind the
observed gap structures in the HL Tau disk.
