Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session L43: New Developments in the FQHE in Halffilled Landau LevelsInvited

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Sponsoring Units: DCMP Room: BCEC 210B 
Wednesday, March 6, 2019 11:15AM  11:51AM 
L43.00001: Observation of halfinteger thermal Hall conductance Invited Speaker: Moty Heiblum Quantum mechanics sets an upper bound on the amount of charge flow as well as on the amount of heat flow in ballistic onedimensional channels. The two relevant upper bounds, that combine only fundamental constants, are the quantum of the electrical conductance, G_{e}=η e^{2}/h with η =e*/e and the quantum of the thermal conductance, G_{th}=k_{0}T=(π^{2}k_{B}^{2}/3h)T [1]. Remarkably, the latter does not depend on particles charge; particles statistics; and even the interaction strength among the particles [2]. 
Wednesday, March 6, 2019 11:51AM  12:27PM 
L43.00002: Fractional Quantized Hall States with Even Denominator Invited Speaker: Bertrand I. Halperin Evendenominator fractional quantized Hall states have been seen in a variety of systems. In addition to the wellknown states at filling fractions ν = 5/2 and 7/2 observed in GaAs narrow wells, evendenominator quantized states have been seen in Bernalstacked bilayer graphene, in ZnO, and in GaAs double layers and wide quantum wells at total filling ν_{total} = ½. The precise nature of the quantized Hall states is a matter of debate in all these cases, and I will discuss some of the alternative theories. There is another case, however, where the situation is clear. Recent experiments on a system of two graphene layers separated by a thin insulator find, among other states, a quantized Hall state with filling ν = ¼ in each layer. Measurements of a quantized Hall drag, as well as quantized Hall resistance, show that the system has the characteristics of the 331 Abelian state.^{1} [1] Xiaomeng Liu, Zeyu Hao, K. Watanabe, T. Taniguchi, B. Halperin, and P. Kim, arXiv:1810.08681. 
Wednesday, March 6, 2019 12:27PM  1:03PM 
L43.00003: Theory of disorderinduced halfinteger thermal Hall conductance Invited Speaker: David Mross Thermal Hall conductance in the halffilled first Landau level was recently measured to take the quantized noninteger value kappa=5/2, which indicates a nonAbelian phase of matter. Such exotic states have long been predicted to arise at this filling factor, but the measured value disagrees with numerical studies, which predict kappa=3/2 or 7/2. I will briefly review the contradictory experimental and theoretical findings and discuss how they may be reconciled. Specifically, I will describe a possible resolution based on disorderinduced formation of mesoscopic puddles. Interactions between these puddles can generate a coherent macroscopic state that exhibits a plateau with quantized kappa=5/2 and nonAbelian quasiparticles that are distinct from those of the microscopic puddles. 
Wednesday, March 6, 2019 1:03PM  1:39PM 
L43.00004: Even denominator fractional quantum Hall physics in higher order Landau levels of graphene Invited Speaker: Jurgen Smet An important development in the field of the fractional quantum Hall effect has been the proposal that the 5/2 state observed in the Landau level with orbital index n = 1 of twodimensional electrons in a GaAs quantum well originates from a chiral pwave paired state of composite fermions which are topological bound states of electrons and quantized vortices. This state is theoretically described by a ``Pfaffian" wave function or its hole partner called the antiPfaffian, whose excitations are neither fermions nor bosons but Majorana quasiparticles obeying nonAbelian braid statistics. This has inspired innovative ideas for computation and has also instigated a quest for other states with exotic quasiparticles. Here we report experiments on monolayer graphene that show clear evidence for unexpected evendenominator fractional quantum Hall physics in the n = 3 Landau level. We numerically investigated the known candidate states for evendenominator fractional quantum Hall effect, including the Pfaffian, the particlehole symmetric Pfaffian, the 221parton, and several valley/spin singlet states. We conclude that, among these, the 221parton state is a possible candidate to explain the experimentally observed state and that this incompressible ground state is distinct from the 5/2 state in GaAs . Like the Pfaffian, this state is also believed to harbour quasiparticles with nonAbelian braid statistics. 
Wednesday, March 6, 2019 1:39PM  2:15PM 
L43.00005: The Dirac Composite Fermion of the Fractional Quantum Hall Effect Invited Speaker: Dam Thanh Son TBD 
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