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The chiral edge current is the boundary manifestation of the Chern number ofa quantum anomalous Hall (QAH) insulator. Its direct observation is assumed torequire well-quantized Hall conductance, and is so far lacking. The recentlydiscovered van der Waals antiferromagnet MnBi$_2$Te$_4$ is theorized as a QAHin odd-layers but has shown Hall resistivity below the quantization value atzero magnetic field. Here, we perform scanning superconducting quantuminterference device (sSQUID) microscopy on these seemingly failed QAHinsulators to image their current distribution. When gated to the chargeneutral point, our device exhibits edge current, which flows unidirectionallyon the odd-layer boundary both with vacuum and with the even-layer. Thechirality of such edge current reverses with the magnetization of the bulk.Surprisingly, we find the edge channels coexist with finite bulk conductioneven though the bulk chemical potential is in the band gap, suggesting theirrobustness under significant edge-bulk scattering. Our result establishes theexistence of chiral edge currents in a topological antiferromagnet and offersan alternative for identifying QAH states.

Direct observation of chiral edge current at zero magnetic field in odd-layer MnBi$_2$Te$_4$