Quantum Transport in Black Phosphorus Two-dimensional Hole Gas in High Magnetic Fields

Black phosphorus has recently emerged as a new two-dimensional (2D) material with a direct bandgap and high carrier mobilities. In this talk we present our transport study of black phosphorus 2D hole gas in high magnetic fields. We observe well-defined quantized plateaus in Hall resistance, accompanied by vanishing magnetoresistance; both are hallmarks of the quantum Hall effect. More importantly, we observed, for the first time, new states at fractional filling factors that originate from the strong anisotropy in black phosphorus. We will discuss the link between the new states and the charge density wave states observed in conventional 2D electron systems.