Surface Transport and Quantum Hall Effect in Ambipolar Black Phosphorus Double Quantum Wells

TL;DR

This paper demonstrates the formation of ambipolar double quantum wells in black phosphorus, revealing fully spin-polarized quantum Hall states and highlighting the potential of 2D semiconductors for novel quantum device applications.

Contribution

It introduces a new method to create wide, ambipolar double quantum wells in black phosphorus, enabling tunable charge regimes and revealing enhanced g-factors in quantum Hall states.

Findings

Observation of fully spin-polarized quantum Hall states

Enhanced Lande g-factor due to exchange interactions

Demonstration of ambipolar tunability in black phosphorus QWs

Abstract

Quantum wells constitute one of the most important classes of devices in the study of 2D systems. In a double layer QW, the additional "which-layer" degree of freedom gives rise to celebrated phenomena such as Coulomb drag, Hall drag and exciton condensation. Here we demonstrate facile formation of wide QWs in few-layer black phosphorus devices that host double layers of charge carriers. In contrast to tradition QWs, each 2D layer is ambipolar, and can be tuned into n-doped, p-doped or intrinsic regimes. Fully spin-polarized quantum Hall states are observed on each layer, with enhanced Lande g-factor that is attributed to exchange interactions. Our work opens the door for using 2D semiconductors as ambipolar single, double or wide QWs with unusual properties such as high anisotropy.