Quantum hall effect goes 3D: scientists unveil new topological state in weyl semimetals

The quantum anomalous Hall effect (QAHE) is one of the most important phenomena in condensed matter physics, holding significant promise in low-energy-dissipation electronics that could possibly revolutionize the next-generation information technology. So far, QAHE has been limited to two-dimensional systems, leaving its three-dimensional counterpart as a missing piece in the Hall effect family.

In a new study, researchers from Fudan University, Nankai University, and other institutions fill this gap by proposing a 3D QAHE in WSMs. WSMs are topological materials known for their exotic Weyl nodes and Fermi arc surface states. The team introduced Rashba spin-orbit coupling into a time-reversal-symmetry-broken WSM model, creating a system with a quantized Chern number of 1.

Using different theoretical modeling, they calculate the bulk and surface band structures, confirming the presence of unique boundary states: two chiral surface states along one spatial direction, a pair of Fermi-energy-dependent chiral hinge states along another, and additional chiral surface states connecting them along the third direction. This 3D bulk-boundary correspondence distinguishes the system from stacked 2D Chern insulators.

Remarkably, the transport properties are highly anisotropic. Depending on the current direction and Fermi energy, the Hall resistance quantizes to 0, h/e², or ±h/e². These features are verified through Landauer-Büttiker transport calculations, showing robustness against disorder.

This discovery not only completes the Hall effect family in three dimensions but also holds promise for applications in low-power topological electronics, programmable devices, and in-memory computing. The team suggests experimental realization in magnetically doped WSMs.

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