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Title: Why zero-field quantized Hall effects survive only near one kelvin
Plain: Magnetic topological insulators show a perfectly quantized Hall resistance only at temperatures of order one kelvin, far below the temperature at which they become magnetic, and the reason is debated.
Precise: In Cr- or V-doped (Bi,Sb)2Te3 films and odd-layer MnBi2Te4 flakes, full quantum anomalous Hall quantization ($R_{xy} = h/e^2, R_{xx} \to 0$) appears only at $T$ of order 1 K, while magnetic order sets in at 10-30 K and spectroscopic exchange gaps of tens of meV are reported. Identify the mechanism limiting the quantization temperature (magnetic disorder and gap inhomogeneity, antisite defects, surface-gap fluctuations, parallel bulk conduction) and predict how to raise it. An answer quantitatively links measured disorder to the transport activation gap.
Settled by: Local imaging of the exchange gap correlated with transport activation energies across samples, reproducing the quantization temperature.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: open
Status note: (empty)
Posed since: (empty)