Topology of many-body edge and extended quantum states in an open spin chain: 1/3 plateau, Kosterlitz-Thouless transition, and Luttinger liquid
R. R. Montenegro-Filho, Fernanda S. Matias, M. D. Coutinho-Filho
Abstract
Quantum many-body edge and extended magnon excitations from the 1/3 plateau of the anisotropic Heisenberg model on an open ${AB}_{2}$ chain in a magnetic field $h$ are unveiled using the density matrix renormalization group and exact diagonalization. By tuning both the anisotropy and $h$ in the rich phase diagram, the edge states penetrate in the bulk, whose gap closes in a symmetry-protected topological Kosterlitz-Thouless transition. Also, we witness the squeezed chain effect, the breaking of the edge state degeneracy, and a topological change of the excitations from gapped magnons with quadratic long-wavelength dispersion to a linear spinon dispersion in the Luttinger liquid gapless phase as the anisotropy $\ensuremath{\lambda}$ approaches the critical point from the $\ensuremath{\lambda}>0$ side of the phase diagram.