Abstract

We study translationally invariant spin chains where each unit cell contains an n-state projective representation of a Z(n) x Z(n) internal symmetry, generalizing the spin-1/2 XYZ chain. Such spin chains possess a generalized Lieb-Schultz-Mattis (LSM) constraint, and we demonstrate that certain (n - 1)-component Luttinger liquids possess the correct anomalies to satisfy these LSM constraints. For n = 3, using both numerical and analytical approaches, we find that such spin chains with nearest-neighbor interactions appear to be gapless for a wide range of microscopic parameters and described by a two-component conformally invariant Luttinger liquid. This implies the emergence of n - 1 conserved U(1) charges from only discrete microscopic symmetries. Remarkably, the system remains gapless for an unusually large parameter regime despite the apparent existence of symmetryallowed relevant operators in the field theory. This suggests that either these spin chains have hidden conserved quantities not previously identified, or the parameters of the field theory are simply unusual due to frustration effects of the lattice Hamiltonian. We argue that similar features are expected to occur in (1) Z(n) x Z(n) symmetric chains for n odd and (2) S-n x Z(n) symmetric chains for all n > 2. Finally, we suggest the possibility of a lower bound growing with n on the minimum central charge of field theories that possess such LSM anomalies.

Publication Details
Publication Type
Journal Article
Year of Publication
2021
Volume
104
DOI
10.1103/PhysRevB.104.045151
Journal
Physical Review B
Contributors