Quantum Hall ferromagnetic transitions are typically achieved by increasing the Zeeman energy through in-situ sample rotation, while transitions in systems with pseudo-spin indices can be induced by gate control. We report here a gate-controlled quantum Hall ferromagnetic transition between two real spin states in a conventional two-dimensional system without any in-plane magnetic field. We show that the ratio of the Zeeman splitting to the cyclotron gap in a Ge two-dimensional hole system increases with decreasing density owing to inter-carrier interactions. Below a critical density of ∼2.4×1010 cm−2, this ratio grows greater than 1, resulting in a ferromagnetic ground state at filling factor ν=2. At the critical density, a resistance peak due to the formation of microscopic domains of opposite spin orientations is observed. Such gate-controlled spin-polarizations in the quantum Hall regime opens the door to realizing Majorana modes using two-dimensional systems in conventional, low-spin-orbit-coupling semiconductors.
@article{arxiv.1706.02044,
title = {Density-controlled quantum Hall ferromagnetic transition in a two-dimensional hole system},
author = {T. M. Lu and L. A. Tracy and D. Laroche and S. -H. Huang and Y. Chuang and Y. -H. Su and J. -Y. Li and C. W. Liu},
journal= {arXiv preprint arXiv:1706.02044},
year = {2017}
}