  Quantum spin liquids represent exotic states of spin systems characterized by
long-range entanglement and emergent fractionalized quasiparticles. It is
generally believed that disorder is hostile to quantum spin liquids. In our
study, we investigated the magnetic properties of a kagome system,
YCu$_3$(OH)$_6$[(Cl$_x$Br$_{1-x}$)$_{3-y}$(OH)$_{y}$]. Within this system, some
of the hexagons exhibit alternate bonds along the Cu-O-Cu exchange paths, while
others remain uniform. We found that a long-range antiferromagnetic order
emerges when uniform hexagons dominate. Conversely, possible
quantum-spin-liquid state arises when the number of alternate-bond hexagons
exceeds about 2/3. Therefore, the alternate-bond hexagons, typically considered
as disorders, actually serve as the building blocks of the quantum spin liquid
in this system. Notably, the low-temperature properties of the quantum spin
liquid are directly associated with the height of the out-of-plane yttrium
ions, which may be linked to changes in superexchange energies. Our results
suggest that understanding the magnetic ground states in this system lies
beyond the theoretical framework of the Heisenberg model constructed on the
kagome lattice.
