Kavli Affiliate: Jing Wang
| First 5 Authors: Jinjiang Zhu, Yang Feng, Xiaodong Zhou, Yongchao Wang, Zichen Lian
| Summary:
The chiral edge current is the boundary manifestation of the Chern number of
a quantum anomalous Hall (QAH) insulator. Its direct observation is assumed to
require well-quantized Hall conductance, and is so far lacking. The recently
discovered van der Waals antiferromagnet MnBi$_2$Te$_4$ is theorized as a QAH
in odd-layers but has shown Hall resistivity below the quantization value at
zero magnetic field. Here, we perform scanning superconducting quantum
interference device (sSQUID) microscopy on these seemingly failed QAH
insulators to image their current distribution. When gated to the charge
neutral point, our device exhibits edge current, which flows unidirectionally
on the odd-layer boundary both with vacuum and with the even-layer. The
chirality of such edge current reverses with the magnetization of the bulk.
Surprisingly, we find the edge channels coexist with finite bulk conduction
even though the bulk chemical potential is in the band gap, suggesting their
robustness under significant edge-bulk scattering. Our result establishes the
existence of chiral edge currents in a topological antiferromagnet and offers
an alternative for identifying QAH states.
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