Colloidal topological insulators

TL;DR

This paper demonstrates a colloidal topological insulator where magnetic colloids exhibit robust edge transport and spin Hall-like effects, opening new avenues for particle manipulation in lab-on-a-chip technologies.

Contribution

It introduces the first experimental realization of a colloidal topological insulator with topologically protected edge states in a classical particle system.

Findings

Colloids travel along edges with skipping orbits.

Edge transport is robust against perturbations.

Observation of spin Hall-like effect with paramagnetic and diamagnetic colloids.

Abstract

Topological insulators insulate in the bulk but exhibit robust conducting edge states protected by the topology of the bulk material. Here, we design a colloidal topological insulator and demonstrate experimentally the occurrence of edge states in a classical particle system. Magnetic colloidal particles travel along the edge of two distinct magnetic lattices. We drive the colloids with a uniform external magnetic field that performs a topologically non-trivial modulation loop. The loop induces closed orbits in the bulk of the magnetic lattices. At the edge, where both lattices merge, the colloids perform skipping orbits trajectories and hence edge-transport. We also observe paramagnetic and diamagnetic colloids moving in opposite directions along the edge between two inverted patterns; the analogue of a quantum spin Hall effect in topological insulators. We present a new, robust, and versatile way of transporting colloidal particles, enabling new pathways towards lab on a chip applications.