F. Essler

Criticality enabled long-range order in a U(1)-symmetric spin-1 Heisenberg chain with biquadratic interactions

In a recent paper Nahum argued on the basis of a renormalization-group analysis that, contrary to standard lore, ground states of 1D spin chains with short-range interactions can spontaneously break U(1) ``easy-plane''spin rotation symmetry. True long-range order of $(S^x,S^y)$ arises at the phase transition between tw...