title: The half-filled Landau level: The case for Dirac composite fermions.
abstract: In a two-dimensional electron gas under a strong magnetic field, correlations generate emergent excitations distinct from electrons. It has been predicted that "composite fermions"--bound states of an electron with two magnetic flux quanta--can experience zero net magnetic field and form a Fermi sea. Using infinite-cylinder density matrix renormalization group numerical simulations, we verify the existence of this exotic Fermi sea, but find that the phase exhibits particle-hole symmetry. This is self-consistent only if composite fermions are massless Dirac particles, similar to the surface of a topological insulator. Exploiting this analogy, we observe the suppression of 2k(F) backscattering, a characteristic of Dirac particles. Thus, the phenomenology of Dirac fermions is also relevant to two-dimensional electron gases in the quantum Hall regime.
authors.affiliation: Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Geraedts
authors.affiliation: Station Q, Microsoft Research, Santa Barbara, CA 93106, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Zaletel
authors.affiliation: Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125, USA. Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA. Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Roger S K
authors.initials: RS
authors.lastname: Mong
authors.affiliation: Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada. Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Max A
authors.initials: MA
authors.lastname: Metlitski
authors.affiliation: Department of Physics, University of California, Berkeley, CA 94720, USA. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Ashvin
authors.initials: A
authors.lastname: Vishwanath
authors.affiliation: Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125, USA. Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, CA 91125, USA. motrunch@caltech.edu.
authors.forename: Olexei I
authors.initials: OI
authors.lastname: Motrunich