Condensed Matter Seminar: Hart Goldman

Dirac Composite Fermions and Emergent Reflection Symmetry about Even Denominator Filling Fractions
Motivated by the appearance of a “reflection symmetry” in transport experiments and the absence of statistical periodicity in relativistic quantum field theories, we propose a series of relativistic composite fermion theories for the compressible states appearing at filling fractions ν = 1 / 2 n in quantum Hall systems. These theories consist of electrically neutral Dirac fermions attached to 2 n flux quanta via an emergent Chern-Simons gauge field. While not possessing an explicit particle-hole symmetry, these theories reproduce the known Jain sequence states proximate to ν = 1 / 2 n, and we show that such states can be related by the observed reflection symmetry, at least at mean-field level. We further argue that the lowest Landau level limit requires that the Dirac fermions be tuned to criticality, whether or not this symmetry extends to the compressible states themselves.