Entanglement spectra of non-chiral topological (2+1)-dimensional phases with strong time-reversal breaking, Li-Haldane state counting, and PEPS

TL;DR

This paper investigates the entanglement spectra of non-chiral topological phases with strong symmetry breaking, revealing chiral-like features that can mislead phase identification, and analyzes their detailed structure in an $SU(3)$ PEPS model.

Contribution

It demonstrates how non-chiral topological states with symmetry breaking can exhibit chiral-like entanglement spectra, and provides a detailed analysis of their sector-dependent structure in an $SU(3)$ PEPS.

Findings

Low-lying entanglement spectra can mimic chiral phase counting.

Distinct differences in spectra across sectors reveal non-chiral nature.

Entanglement spectra contain irreps of $SU(3)$ from combined chiral sectors.

Abstract

The Li-Haldane correspondence [PRL 101, 010504 (2008)] is often used to help identify wave functions of (2+1)-D chiral topological phases (i.e., with non-zero chiral central charge) by studying low-lying entanglement spectra (ES) on long cylinders of finite circumference. Here we consider such ES of states [in fact, certain Projected Entangled Pair States (PEPS)] that are not chiral (i.e., having zero chiral central charge), but which strongly break time-reversal as well as reflection symmetry, while preserving their product, the same symmetry as a chiral state. This leads to ES with branches of both right- and left-moving chiralities, but with vastly different velocities. For circumferences much smaller than the inverse entanglement gap scale, the low-lying ES appear chiral in some topological sectors, and precisely follow the Li-Haldane state counting of a truly chiral phase. This could lead one to misidentify the phase as chiral. However, considering the ES in all sectors, one can observe distinct differences from a chiral phase. We explore this in an $SU(3)$ spin liquid PEPS studied by Kure\v{c}i\'c, et al. [PRB 99, 045116 (2019)], where the topologically trivial sector has the state counting of a chiral $SU(3)$-level-one [$SU(3)_1$] Conformal Field Theory (CFT). In fact, the PEPS has $D(\mathbb{Z}_3)$ topological order, with 9 sectors. We compute the ES in minimally entangled states corresponding to these sectors, which map to the 9 anyon types of doubled $SU(3)_1$ Chern-Simons Topological Field Theory. The state countings of the ES coincide with our expectation: the ES contain irreps of global $SU(3)$ symmetry from the tensor products of the (lowest-lying) irrep of primary states of a "high-velocity" chiral $SU(3)_1$ CFT with the full content of a "low-velocity" chiral $SU(3)_1$ CFT sector, a non-chiral structure beyond that observable in the topologically trivial sector of the ES.