Magnetization Plateaus in Spin Chains: “Haldane Gap” for Half-Integer Spins
Magnetization Plateaus in Spin Chains: “Haldane Gap” for Half-Integer Spins
We discuss zero-temperature quantum spin chains in a uniform magnetic field, with axial symmetry. For integer or half-integer spin, $S$, the magnetization curve can have plateaus and we argue that the magnetization per site $m$ is topologically quantized as $q (S - m)= integer$ at the plateaus, where $q$ is …