There is a lot of interest in finding and identifying novel
quantum materials. We here focus on d1 materials with a
strong spin-orbit coupling, which are supposed to realize a much
higher symmetry than SU(2), an emergent SU(4) symmetry [1,2].
In fact, α-ZrCl3 is expected to host the SU(4) Heisenberg model
on the honeycomb lattice with a large frustration . These
SU(4) materials potentially realize a new type of spin liquids,
a gapped Z4 spin liquid . We present new density matrix
renormalization group (DMRG) studies on the SU(4)
Heisenberg model on the honeycomb lattice to show that
the ground state is indeed gapped and symmetric
with respect to all the symmetries, indicating
the existence of a gapped spin liquid in this
system . The topological entanglement entropy
is close to the expected value for the Z4 spin liquid,
which has 16 superselection sectors in the thermodynamic limit.
 M.G.Y., M. Oshikawa, and G. Jackeli, Phys. Rev. Lett. 121, 097201 (2018).
 M.G.Y., M. Oshikawa, and G. Jackeli, Phys. Rev. B 104, 224436 (2021).
 P. Corboz et al., Phys. Rev. X 2, 041013 (2012).
 M.G.Y., and S. Fujimoto, arXiv:2111.14470 (2021).
 M.G.Y., K. Penc, and F. Pollmann, to appear.