# Photo-induced SU(3) topological material of spinless fermions

## TL;DR

This paper proposes a method to realize SU(3) topological phases in spinless fermions through a tripartite lattice with engineered gauge fields and Zeeman-like terms, revealing new topological states without breaking time-reversal symmetry.

## Contribution

It identifies key ingredients for SU(3) topological phases and demonstrates how to engineer them in a lattice system using photon polarization and gauge fields.

## Key findings

- SU(3) topological phases require entangled components with opposite chirality.
- A tripartite lattice with site-selective photon polarization can realize the necessary conditions.
- Finite Chern number achieved without breaking time-reversal symmetry.

## Abstract

Generation of topological phases of matter with SU(3) symmetry in a condensed matter setup is challenging due to the lack of an intrinsic three-fold chirality of quasiparticles. We uncover two salient ingredients required to express a three-component lattice Hamiltonian in a SU(3) format with non-trivial topological invariant. We find that all three SU(3) components must be entangled via a gauge field, with opposite chirality between any two components, and there must be band inversions between all {\it three} components in a given eigenstate. For spinless particles, we show that such chiral states can be obtained in a tripartite lattice with three inequivalent lattice sites in which the Bloch phase associated with the nearest neighbor hopping acts as $k$-space gauge field. The second and a more crucial criterion is that there must also be an odd-parity Zeeman-like term, i.e. $\sin(k)\sigma_z$ term where $\sigma_z$ is the third Pauli matrix defined in any two components of the SU(3) basis. Solving the electron-photon interaction term in a periodic potential with a modified tight-binding model, we show that such a term can be engineered with site-selective photon polarization. Such site selective polarization can be obtained in multiple ways, such as using Sisyphus cooling technique, polarizer plates, etc. With the $k$-resolved Berry curvature formalism, we delineate the relationship between the SU(3) chirality, band inversion, and $k$-space monopoles, governing finite Chern number without breaking the time-reversal symmetry. The topological phase is affirmed by edge state calculation, obeying the bulk-boundary correspondence.