University of Hong Kong Finds Hall Conductance at Half-Integer Values

Researchers at The University of Hong Kong have identified a quantum phenomenon where Hall conductance exhibits values at half-integer levels, rather than the traditionally quantized resistance. This discovery challenges established understandings of the quantum Hall effect, typically observed in insulating materials, as it occurs within two-dimensional ferromagnetic semimetals possessing finite longitudinal conduction. Shun-Qing Shen and collaborators found that a single massless Dirac cone, rather than previously theorized massive Dirac fermions, is the origin…