Spin Reversal of a Quantum Hall Ferromagnet at a Landau Level Crossing

Abstract

When Landau levels (LLs) become degenerate near the Fermi energy in the quantum Hall regime, interaction effects can drastically modify the electronic ground state. We study the quantum Hall ferromagnet formed in a two-dimensional hole gas around the LL filling factor $\nu =1$ in the vicinity of a LL crossing in the heave-hole valence band. Cavity spectroscopy in the strong-coupling regime allows us to optically extract the two-dimensional hole gas' spin polarization. By analyzing this polarization as a function of hole density and magnetic field, we observe a spin flip of the ferromagnet. Furthermore, the depolarization away from $\nu =1$ accelerates close to the LL crossing. This is indicative of an increase in the size of Skyrmion excitations as the effective Zeeman energy vanishes at the LL crossing.

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• The Ferroelectric Photo-Groundstate of SrTiO${}_3$: Cavity Materials Engineering
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• Topological Lifshitz transition and one-dimensional Weyl mode in HfTe5
• Robust Quantum Hall Ferromagnetism near a Gate-Tuned ν = 1 Landau Level Crossing
• Spin-selective strong light-matter coupling in a 2D hole gas-microcavity system
• Competing Many-Body Phases at Small Fillings in Ultrahigh-Quality GaAs 2D Hole Systems: Role of Landau Level Mixing
• Ferromagnetism and Skyrmions in the Hofstadter-Fermi-Hubbard Model
• Even-denominator fractional quantum Hall states with spontaneously broken rotational symmetry
• Spin polarization of Quantum Hall states for filling factors 1 < v < 2 measured with microcavity polaritons