Equilibration and Filtering of Quantum Hall Edge States in Few-Layer Black Phosphorus

TL;DR

This study investigates how quantum Hall edge states in few-layer black phosphorus can be controlled and filtered using p-p'-p junctions, revealing tunable equilibration and spin-dependent transmission properties.

Contribution

It introduces a method to realize and analyze p-p'-p junctions in black phosphorus, demonstrating gate-tunable edge channel transmission and spin-dependent equilibration behaviors.

Findings

Full and partial equilibration of edge states observed.

Inner low-doping region acts as a tunable filter.

Edge channel transmission is controllable via gating.

Abstract

We realize p-p'-p junctions in few-layer black phosphorus (BP) devices, and use magneto-transport measurements to study the equilibration and transmission of edge states at the interfaces of regions with different charge densities. We observe both full equilibration, where all edge channels equilibrate and are equally partitioned at the interfaces, and partial equilibration, where only equilibration only takes place among modes of the same spin polarization. Furthermore, the inner p'-region with low-doping level in the junction can function as a filter for highly doped p-regions which demonstrates gate-tunable transmission of edge channels.