Projective construction of two-dimensional symmetry-protected topological phases with U(1), SO(3), or SU(2) symmetries

TL;DR

This paper introduces a general method to construct two-dimensional symmetry-protected topological (SPT) phases in lattice systems by fractionalizing spins and bosons into fermions, filling Chern bands, and applying Gutzwiller projection, enabling the realization of various SPT states with different symmetries.

Contribution

The authors develop a projective construction approach to generate 2D SPT states with U(1), SO(3), or SU(2) symmetries using fermionic fractionalization and Gutzwiller projection, extending the toolkit for topological phases.

Findings

Constructed U(1) SPT state for spin-1 models.

Built SO(3) SPT state for bosonic systems.

Developed SU(2) SPT state for spin-1/2 bosons.

Abstract

We propose a general approach to construct symmetry protected topological (SPT) states i.e the short-range entangled states with symmetry) in 2D spin/boson systems on lattice. In our approach, we fractionalize spins/bosons into different fermions, which occupy nontrivial Chern bands. After the Gutzwiller projection of the free fermion state obtained by filling the Chern bands, we can obtain SPT states on lattice. In particular, we constructed a U(1) SPT state of a spin-1 model, a SO(3) SPT state of a boson system with spin-1 bosons and spinless bosons, and a SU(2) SPT state of a spin-1/2 boson system. By applying the "spin gauge field" which directly couples to the spin density and spin current of $S^z$ components, we also calculate the quantum spin Hall conductance in each SPT state. The projective ground states can be further studied numerically in the future by variational Monte Carlo etc.