Valley Stoner instability of the composite Fermi sea
Name
PhysRevB.98.155104.pdf
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676.04 KB
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Author(s)
Zhu, Zheng
Sheng, D. N.
Fu, Liang
Sodemann, Inti
Date Issued
October 2018
Journal
Physical Review B
Publisher
American Physical Society
Citation
Zhu, Zheng et al. "Valley Stoner instability of the composite Fermi sea." Physical Review B 98, 15 (October 2018): 155104 © 2018 American Physical Society
Version
Final published version
Abstract
We study two-component electrons in the lowest Landau level at total filling factor ν[subscript T] = 1/2 with anisotropic mass tensors and principal axes rotated by π/2 as realized in aluminum arsenide (AlAs) quantum wells. Combining exact diagonalization and the density matrix renormalization group we demonstrate that the system undergoes a quantum phase transition from a gapless state in which both flavors are equally populated to another gapless state in which all the electrons spontaneously polarize into a single flavor beyond a critical mass anisotropy of m[subscript x]/m[subscript y]∼7. We propose that this phase transition is a form of itinerant Stoner transition between a two-component and a single-component composite Fermi sea states and describe a set of trial wave functions which successfully capture the quantum numbers and shell filling effects in finite size systems as well as providing a physical picture for the energetics of these states. Our estimates indicate that the composite Fermi sea of AlAs is the analog of an itinerant Stoner magnet with a finite spontaneous valley polarization. We pinpoint experimental evidence indicating the presence of Stoner magnetism in the Jain states surrounding ν = 1/2.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
https://doi.org/10.1103/PhysRevB.98.155104
