Topological chiral kagome lattice

TL;DR

This paper introduces a 3D chiral kagome lattice that maintains key topological features of the 2D kagome, hosts Weyl fermions, and exhibits unique surface states with potential for unconventional transport phenomena.

Contribution

It demonstrates the design and analysis of a 3D chiral kagome lattice with robust topological features and explores material candidates using first-principles calculations.

Findings

Presence of Weyl fermions in the 3D chiral kagome lattice.

Existence of 1D dispersive and flat Fermi arc surface states.

Potential for unconventional non-local transport phenomena.

Abstract

Chirality, a fundamental structural property of crystals, can induce many unique topological quantum phenomena. In kagome lattice, unconventional transports have been reported under tantalizing chiral charge order. Here, we show how by deforming the kagome lattice to obtain a three-dimensional (3D) chiral kagome lattice in which the key band features of the non-chiral 2D kagome lattice - flat energy bands, van Hove singularities (VHSs), and degeneracies - remain robust in both the $k_z$ = 0 and $\pi$ planes in momentum space. Given the handedness of our kagome lattice, degenerate momentum points possess quantized Chern numbers, ushering in the realization of Weyl fermions. Our 3D chiral kagome lattice surprisingly exhibits 1D behavior on its surface, where topological surface Fermi arc states connecting Weyl fermions are dispersive in one momentum direction and flat in the other direction. These 1D Fermi arcs open up unique possibilities for generating unconventional non-local transport phenomena at the interfaces of domains with different handedness, and the associated enhanced conductance as the separation of the leads on the surface is increased. Employing first-principles calculations, we investigate in-depth the electronic and phononic structures of representative materials within the ten space groups that can support topological chiral kagome lattices. Our study opens a new research direction that integrates the advantages of structural chirality with those of a kagome lattice and thus provides a new materials platform for exploring unique aspects of correlated topological physics in chiral lattices.