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 <i>ρ</i>_<i>xy</i> and vertical resistivity <i>ρ</i>_<i>zz</i>. The bulk QHE is attributable to synergetic action between Landau cyclotron movement under magnetic field <i>B</i> and periodically modulated potential due to the nanometer-scaled lamellae. This mechanism would form the fixed number of edge states along <i>B</i>-perpendicular and <i>B</i>-parallel directions respectively, equivalent to stacked 2D-QHE layers, leading to quantized <i>ρ</i>_<i>xy</i> and <i>ρ</i>_<i>zz</i>. Our work verifies that microstructure engineering could result in the coherent transport of electrons and generate new quantum phenomena in bulk materials.