A new study has demonstrated the three-dimensional quantum Hall effect in acoustic waves using a Weyl acoustic crystal, marking the first observation of one-dimensional edge states and opening avenues for advanced acoustic device development.
The quantum Hall effect (QHE) stands as a landmark discovery in condensed matter physics, paving the way for the exploration of topological physics. Advancing QHE into three dimensions presents an exciting yet formidable challenge. The complication stems from the fact that, in three dimensions, Landau levels evolve into bands along the magnetic field direction, which obstructs the formation of bulk gaps.
Recently, a feasible scheme has been proposed in Weyl semimetals, whose Fermi arc states on opposite surfaces are connected through the bulk Weyl points to form a complete Fermi loop, and under the magnetic field, one-dimensional edge states are induced on the boundary of the opposite surface. However, the unique edge states have yet to be experimentally observed.
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