Novel Bulk Quantum Hall Effect in Nanostructured TaP Macroscopic Crystals

Bulk quantum Hall effect (QHE), the natural extension of the two-dimensional (2D) QHE, is one of the representative phenomena of coherent electron transport. However, bulk QHE has rarely been reported in real materials with macroscopic sizes. Here, we report a novel bulk QHE in macroscopic millimeter-sized and nanostructured TaP crystals consisting of nanometer-scale lamellae. Specifically, the simultaneous quantum plateaus were observed in both transverse resistivity ρ_xy and vertical resistivity ρ_zz. The bulk QHE is attributable to synergetic action between Landau cyclotron movement under magnetic field B and periodically modulated potential due to the nanometer-scaled lamellae. This mechanism would form the fixed number of edge states along B-perpendicular and B-parallel directions respectively, equivalent to stacked 2D-QHE layers, leading to quantized ρ_xy and ρ_zz. Our work verifies that microstructure engineering could result in the coherent transport of electrons and generate new quantum phenomena in bulk materials.