Topological nature of higher-order hinge states revealed by spin transport

TL;DR

This study demonstrates the topological nature of hinge states in a 3D higher-order topological semimetal through spin transport measurements, revealing their robustness and helical spin-momentum locking.

Contribution

It provides the first experimental evidence of the topological protection of hinge states in higher-order topological materials using spin potentiometric techniques.

Findings

Hinge states exhibit spin-momentum locking similar to quantum spin Hall states.

Hinge states are robust up to room temperature.

Hinge states can diffuse over 5 micrometers nonlocally.

Abstract

One-dimensional (1D) gapless hinge states are predicated in the three-dimensional (3D) higher-order topological insulators and topological semimetals, because of the higher-order bulk-boundary correspondence. Nevertheless, the topologically protected property of the hinge states is still not demonstrated so far, because it is not accessible by conventional methods, such as spectroscopy experiments and quantum oscillations. Here, we reveal the topological nature of hinge states in the higher-order topological semimetal Cd3As2 nanoplate through spin potentiometric measurements. The results of current induced spin polarization indicate that the spin-momentum locking of the higher-order hinge state is similar to that of the quantum spin Hall state, showing the helical characteristics. The spin-polarized hinge states are robust up to room temperature and can nonlocally diffuse a long distance larger than 5 {\mu}m, further indicating their immunity protected by topology. Our work deepens the understanding of transport properties of the higher-order topological materials and should be valuable for future electronic and spintronic applications.