Mesoscopic Transport of Quantum Anomalous Hall Effect in Sub-Micron Size Regime

TL;DR

This study investigates mesoscopic transport phenomena in sub-micron quantum anomalous Hall devices, revealing how device size influences back-scattering, resistance fluctuations, and edge state confinement, advancing understanding of quantum transport at small scales.

Contribution

It provides new insights into mesoscopic transport mechanisms and edge state confinement in sub-micron QAH devices, which were not previously well understood.

Findings

Back-scattering channels form via percolative hopping between puddles.

Large resistance fluctuations occur near coercive fields in narrow devices.

Chiral edge states are confined within a Fermi wavelength at device boundaries.

Abstract

The quantum anomalous Hall (QAH) effect has been demonstrated in two-dimensional topological insulator systems incorporated with ferromagnetism. However, a comprehensive understanding of mesoscopic transport in sub-micron QAH devices has yet been established. Here we fabricated miniaturized QAH devices with channel widths down to 600 nm, where the QAH features are still preserved. A back-scattering channel is formed in narrow QAH devices through percolative hopping between 2D compressible puddles. Large resistance fluctuations are observed in narrow devices near the coercive field, which is associated with collective interference between intersecting paths along domain walls when the device geometry is smaller than the phase coherence length $L_\phi$. Through measurement of size-dependent breakdown current, we confirmed that the chiral edge states are confined at the physical boundary with its width on the order of Fermi wavelength.