Lecturer: Jei Wang
Abstract
Interacting electrons in high magnetic fields exhibit rich physical
phenomena including the gapped fractional quantum Hall effects and the
gapless states. The composite Fermi liquids (CFLs) are gapless states
that can occur at even denominator Landau level fillings. Due to the
celebrated work of Halperin, Lee and Read (94), the CFLs were
understood as Fermi liquids of composite fermions, which are bound
states of electron and electromagnetic flux quanta. However, at 1/2
filling, it is not obvious why the HLR description is consistent with
the particle hole symmetry. Motivated by this, recently Son (15)
proposed an alternative description for CFLs at 1/2, according to
which the composite fermions are instead emergent Dirac fermions.
Importantly, Son’s theory predicts a Pi Berry curvature singularity at
the composite Fermi sea center. In the first part of this talk [2,3],
I will present our numerical work about detecting this Z2 Berry phase
at 1/2 filling. In the second part [1], I will present how and why
Dirac fermions can emerge at all the other filling fractions (1/2m and
1-1/2m when m is integer) even without the particle hole symmetry.
[1] arXiv 1808.07529. JW.
[2] arXiv 1711.07864. Geraedts, JW, Rezayi, Haldane.
[3] arXiv 1710.09729. JW, Geraedts, Rezayi, Haldane.