2D and 3D topological insulators with isotropic and parity-breaking Landau levels

TL;DR

This paper explores topological insulators in 2D and 3D with harmonic potentials and strong spin-orbit coupling, revealing Landau-level-like quantization, flat energy bands, and topologically protected edge states, potentially realizable with ultra-cold atoms.

Contribution

It introduces a new class of topological insulators with harmonic confinement and spin-orbit coupling, demonstrating Landau-level-like states with flat bands and topological surface states in 2D and 3D.

Findings

Landau-level-like quantization with rotational symmetry

Nearly flat energy bands within each Landau level

Presence of topologically protected edge and surface states

Abstract

We investigate topological insulating states in both two and three dimensions with the harmonic potential and strong spin-orbit couplings breaking the inversion symmetry. Landau-level like quantizations appear with the full 2D and 3D rotational symmetry and time-reversal symmetry. Inside each band, states are labeled by their angular momenta over which energy dispersions are strongly suppressed by spin-orbit coupling to nearly flat. The radial quantization generates energy gaps between neighboring bands at the order of the harmonic frequency. Helical edge or surface states appear on open boundaries characterized by the Z2 index. These Hamiltonians can be viewed from the dimensional reduction of the high dimensional quantum Hall states in 3D and 4D flat spaces. These states can be realized with ultra-cold fermions inside harmonic traps with the synthetic gauge fields.