Bulk and edge spin transport in topological magnon insulators

TL;DR

This paper studies how spin currents flow in a topological magnon insulator, revealing a size-dependent crossover from bulk to edge-dominated transport, with implications for topological bosonic systems.

Contribution

It introduces a phenomenological model for spin transport in topological magnon insulators, highlighting the crossover between bulk and edge transport regimes.

Findings

Bulk and edge spin transport have distinct length scales.

Transport behavior transitions from bulk-dominated to edge-dominated with increasing system size.

Results are applicable to topological transport in nonconserved bosonic systems.

Abstract

We investigate the spin transport properties of a topological magnon insulator, a magnetic insulator characterized by topologically nontrivial bulk magnon bands and protected magnon edge modes located in the bulk band gaps. Employing the Landau-Lifshitz-Gilbert phenomenology, we calculate the spin current driven through a normal metal$|$topological magnon insulator$|$normal metal heterostructure by a spin accumulation imbalance between the metals, with and without random lattice defects. We show that bulk and edge transport are characterized by different length scales. This results in a characteristic system size where the magnon transport crosses over from being bulk-dominated for small systems to edge-dominated for larger systems. These findings are generic and relevant for topological transport in systems of nonconserved bosons.