Title: Six magnetization plateau phases in a kagome antiferromagnet with $\rm{Y}_3\rm{Cu}_9(\rm{OH})_{19}\rm{Cl}_8$-type distortion

Abstract: A recently discovered kagome antiferromagnet $\rm{Y}_3\rm{Cu}_9(\rm{OH})_{19}\rm{Cl}_8$ has attracted significant interest due to its unique kagome lattice structure and magnetic properties. Two separate studies have proposed distinct sets of exchange interaction parameters for this compound. In this study, we investigate the ground state of the spin-1/2 Heisenberg kagome model with three types of nearest-neighbor exchange interactions under a magnetic field by exact diagonalization using the Lanczos method. We reveal that clear magnetization plateaus at $M/M_{\rm sat}$=1/3, 5/9, and 7/9 are present under both parameter sets, which are identified as magnon crystal states based on their spin structures. Our findings suggest that these plateaus could potentially be experimentally confirmed with magnetization measurements on $\rm{Y}_3\rm{Cu}_9(\rm{OH})_{19}\rm{Cl}_8$ under a magnetic field of approximately 300 T. Due to the uncertainty in the exchange interactions of $\rm{Y}_3\rm{Cu}_9(\rm{OH})_{19}\rm{Cl}_8$, we perform additional calculations by varying these interactions. Consequently, we discover additional plateau phases at $M/M_{\rm sat}$=1/3, 5/9, and 7/9, each distinctly different from the magnon crystal states.