Bloch ferromagnetism of composite fermions

Md Shafayat Hossain, Tongzhou Zhao, Songyang Pu, M. A. Mueed, M. K. Ma, K. A. Villegas Rosales, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, J. K. Jain, M. Shayegan

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


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 energy1. However, experimental realizations of this effect have been hard to implement. Here, we report the observation of an abrupt, interaction-driven transition to full magnetization, highly reminiscent of Bloch ferromagnetism. Our platform utilizes the two-dimensional Fermi sea of composite fermions near half-filling of the lowest Landau level. We measure the Fermi wavevector—which directly provides the spin polarization—and observe a sudden transition from a partially spin-polarized to a fully spin-polarized ground state as we lower the density of the composite fermions. Our theoretical calculations that take Landau level mixing into account provide a semi-quantitative account of this phenomenon.

Original languageEnglish (US)
Pages (from-to)48-52
Number of pages5
JournalNature Physics
Issue number1
StatePublished - Jan 2021
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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