2020/08/17 by Md Shafayat Hossain, Md. Shafayat Hossain, Tongzhou Zhao +10 · 1 citation
Physics and Astronomy · #Composite fermion #Electron #Fermi Gamma-ray Space Telescope #Fermi energy #Fermion #Ferromagnetism #Landau quantization #Magnetic properties of thin films #Paramagnetism #Quantum and electron transport phenomena #Spins #Topological Materials and Phenomena #cond-mat.mes-hall #cond-mat.str-el
paper · pdf · doi:10.1038/s41567-020-1000-z
published as Nat. Phys. (2020); Link: https://www.nature.com/articles/s41567-020-1000-z
openalex publication_date 2020/08/17 · openalex created_date 2020/08/21 · arxiv created 2020/08/26 · arxiv updated 2020/08/27 · openalex updated_date 2026/08/06
In 1929 Felix Bloch suggested that the paramagnetic Fermi sea of electrons should make a spontaneous transition to a fully-magnetized state at very low densities, because the exchange energy gained by aligning the spins exceeds the enhancement in the kinetic energy. We report here the observation of an abrupt, interaction-driven transition to full magnetization, highly reminiscent of Bloch ferromagnetism that has eluded experiments for the last ninety years. Our platform is the exotic two-dimensional Fermi sea of composite fermions at half-filling of the lowest Landau level. Via quantitative measurements of the Fermi wavevector, which provides a direct measure of the spin polarization, we observe a sudden transition from a partially-spin-polarized to a fully-spin-polarized ground state as we lower the composite fermions' density. Our detailed theoretical calculations provide a semi-quantitative account of this phenomenon.