  Spin-orbit coupling is an important ingredient to regulate the many-body
physics, especially for many spin liquid candidate materials such as rare-earth
magnets and Kitaev materials. The rare-earth chalcogenides NaYbCh$_2$ (Ch = O,
S, Se) is a congenital frustrating system to exhibit the intrinsic landmark of
spin liquid by eliminating both the site disorders between Na$^{+}$ and
Yb$^{3+}$ ions with the big ionic size difference and the Dzyaloshinskii-Moriya
interaction with the perfect triangular lattice of the Yb$^{3+}$ ions. The
temperature versus magnetic-field phase diagram is established by the
magnetization, specific heat, and neutron-scattering measurements. Notably, the
neutron diffraction spectra and the magnetization curve might provide
microscopic evidence for a series of spin configuration for in-plane fields,
which include the disordered spin liquid state, 120$^{o}$ antiferromagnet, and
one-half magnetization state. Furthermore, the ground state is suggested to be
a gapless spin liquid from inelastic neutron scattering, and the magnetic field
adjusts the spin orbit coupling. Therefore, the strong spin-orbit coupling in
the frustrated quantum magnet substantially enriches low-energy spin physics.
This rare-earth family could offer a good platform for exploring the quantum
spin liquid ground state and quantum magnetic transitions.
