Crystal-symmetry preserving Wannier states for fractional chern insulators

TL;DR

This paper develops a method to construct Wannier states that preserve lattice rotational symmetry in fractional Chern insulators, improving trial wavefunctions and symmetry-based modeling for these topological states.

Contribution

It introduces a modified mapping approach for Wannier states that maintains lattice symmetry, applicable to high Chern number bands and various lattice geometries.

Findings

Constructed Wannier states preserving C4 symmetry on square lattices.

Enhanced trial wavefunctions for fractional Chern insulators.

Applicable to high Chern number and different lattice symmetries.

Abstract

Recently, many numerical evidences of fractional Chern insulator, i.e. the fractional quantum Hall states on lattices, are proposed when a Chern band is partially filled. Some trial wavefunctions of fractional Chern insulators can be obtained by mapping the fractional quantum Hall wavefunctions defined in the continuum onto the lattice through the Wannier state representation (Phys. Rev. Lett. 107, 126803 (2011)) in which the single particle Landau orbits in the Landau levels are identified with the one dimensional Wannier states of the Chern bands with Chern number C = 1. However, this mapping generically breaks the lattice point group symmetry. In this paper, we discuss a general approach of modifying the mapping to accommodate the lattice rotational symmetry. The wavefunctions constructed through this modified mapping should serve as better trial wavefunctions to compare with the numerics and also as the basis for construction of lattice symmetry preserving pseudo-potential formalism for fractional Chern insulators. The focus of this paper shall be mainly on the $C_4$ rotational symmetry of square lattices. Similar analysis can be straightforwardly generalized to triangular or hexagonal lattices with $C_6$ symmetry. We also generalize the discussion to the lattice symmetry of fractional Chern insulators with high Chern number bands.