Electrostatic control of quantum Hall ferromagnetic transition, a step toward reconfigurable network of helical channels

TL;DR

This paper demonstrates local electrostatic control of quantum Hall ferromagnetic transitions in CdTe quantum wells, enabling potential reconfigurable networks of helical channels for advanced quantum applications.

Contribution

It introduces heterostructures with electrostatic gating to control quantum Hall ferromagnetic transitions at fixed magnetic fields, a novel approach for reconfigurable quantum devices.

Findings

Electrostatic gating shifts the QHFm transition at filling factor ν=2.

Control of spin polarization is achieved without changing magnetic field.

Potential for creating reconfigurable helical channel networks.

Abstract

Ferromagnetic transitions between quantum Hall states with different polarization at a fixed filling factor can be studied by varying the ratio of cyclotron and Zeeman energies in tilted magnetic field experiments. However, an ability to locally control such transitions at a fixed magnetic field would open a range of attractive applications, e.g. formation of a reconfigurable network of one-dimensional helical domain walls in a two-dimensional plane. Coupled to a superconductor, such domain walls can support non-Abelian excitation. In this article we report development of heterostructures where quantum Hall ferromagnetic (QHFm) transition can be controlled locally by electrostatic gating. A high mobility two-dimensional electron gas is formed in CdTe quantum wells with engineered placement of paramagnetic Mn impurities. Gate-induced electrostatic field shifts electron wavefunction in the growth direction and changes overlap between electrons in the quantum well and d-shell electrons on Mn, thus controlling the s-d exchange interaction and the field of the QHFm transition. The demonstrated shift of the QHFm transition at a filling factor $\nu=2$ is large enough to allow full control of spin polarization at a fixed magnetic field.