Quantum Hall Effect in Electron-Doped Black Phosphorus Field-Effect Transistors

TL;DR

This paper reports the observation of the quantum Hall effect in high-quality electron-doped black phosphorus FETs, achieved through a novel device design that enhances sample quality and edge channel formation, revealing strong electron interactions.

Contribution

The study introduces a prepatterned graphite local gate to improve black phosphorus 2DEG quality and enables the first observation of quantum Hall effect in electron-doped black phosphorus.

Findings

Quantized Hall plateaus observed in electron-doped black phosphorus.

Large effective mass and enhanced Landé g-factor indicating strong electron interactions.

Potential for exploring exotic many-body quantum states in fractional quantum Hall regime.

Abstract

The advent of black phosphorus field-effect transistors (FETs) has brought new possibilities in the study of two-dimensional (2D) electron systems. In a black phosphorus FET, the gate induces highly anisotropic 2D electron and hole gases. Although the 2D hole gas in black phosphorus has reached high carrier mobilities that led to the observation of the integer quantum Hall effect, the improvement in the sample quality of the 2D electron gas (2DEG) has however been only moderate; quantum Hall effect remained elusive. Here, we obtain high quality black phosphorus 2DEG by defining the 2DEG region with a prepatterned graphite local gate. The graphite local gate screens the impurity potential in the 2DEG. More importantly, it electrostatically defines the edge of the 2DEG, which facilitates the formation of well-defined edge channels in the quantum Hall regime. The improvements enable us to observe precisely quantized Hall plateaus in electron-doped black phosphorus FET. Magneto-transport measurements under high magnetic fields further revealed a large effective mass and an enhanced Land\'e g-factor, which points to strong electron-electron interaction in black phosphorus 2DEG. Such strong interaction may lead to exotic many-body quantum states in the fractional quantum Hall regime.