Triangular lattice (frustrated antiferromagnet)
Classical Néel order (honeycomb)
On the triangular lattice, antiferromagnetic interactions cannot be simultaneously satisfied — any triangle has 3 bonds but only 2 spin states. This geometric frustration prevents magnetic ordering even at T→0, yielding a quantum spin liquid with long-range entanglement but no broken symmetry. Compare to Néel order (honeycomb, bipartite), where every bond is satisfied. Real candidates: herbertsmithite ZnCu₃(OH)₆Cl₂, α-RuCl₃.