Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session G45: Pairing in Fractional Quantum Hall EffectInvited Live Streamed

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Sponsoring Units: DCMP Chair: G. J Sreejith Room: McCormick Place W375D 
Tuesday, March 15, 2022 11:30AM  12:06PM 
G45.00001: Pairing in bilayer quantum Hall systems Invited Speaker: Bertrand I Halperin Among the peculiar quantum Hall states that have been observed in Coulombcoupled bilayer quantum Hall systems, there are a number whose origin depends on some type of pairing between constituent fermions. For example, a fractional quantized state observed in a double layer of graphene separated by insulating hBN, at Landaulevel filling 3/7 in each layer, requires pairing between electronlike composite fermions in one layer and holelike composite fermions in the other. The interlayer coherent quantum Hall state observed in GaAs double quantum wells and in graphene double layers, at total Landaulevel filling 1, may be variously understood as arising from pairing between electrons in one layer and holes in the other, as pwave pairing of composite fermions in opposite layers, or as swave pairing between electron composite fermions in one layer and hole composite fermions in the other. I will discuss these concepts in the context of recent experimental observations and theoretical developments concerning these systems.[14] 
Tuesday, March 15, 2022 12:06PM  12:42PM 
G45.00002: Odd and evendenominator fractional quantum Hall states in monolayer WSe_{2} Invited Speaker: Qianhui Shi Monolayer semiconducting transitionmetal dichalcogenides (TMDs) represent a unique class of twodimensional electron systems. Their atomically thin structure facilitates gate tunability just like graphene does, but unlike graphene, TMDs have the advantage of a sizable band gap and strong spinorbit coupling. Here, through bulk electronic compressibility measurements, we investigate the LL structure of monolayer WSe_{2} in the extreme quantum limit and observe fractional quantum Hall states in the lowest three LLs. The odddenominator fractional quantum Hall sequences demonstrate a systematic evolution with the LL orbital index, consistent with generic theoretical expectations. In addition, we observe an evendenominator state in the second LL that is expected to host nonAbelian statistics. Our results suggest that the 2D semiconductors can provide an experimental platform that closely resembles idealized theoretical models in the quantum Hall regime. 
Tuesday, March 15, 2022 12:42PM  1:18PM 
G45.00003: Graviton Chirality and Topological Order in the Halffilled Landau Level Invited Speaker: Kun Yang Recent work[1] has established that fractional quantum Hall liquids support gravitonlike excitations that carries definitive chirality. We apply this insight to the fractional quantum Hall state at Landau level (LL) filling factor ν = 5/2, which is extremely interesting because it is likely the first nonAbelian state, but its precise nature remains unclear after decades of study. We demonstrate this can be resolved by studying the chirality of its graviton excitations, using circularly polarized Raman scattering [2]. We also discuss the advantage of this bulk probe over the existing edge probes. 
Tuesday, March 15, 2022 1:18PM  1:54PM 
G45.00004: Parton description of nonAbelian paired states Invited Speaker: Ajit Coimbatore Balram The fractional quantum Hall effect (FQHE) forms a paradigm in our understanding of strongly correlated systems. FQHE in the lowest Landau level (LLL) predominantly occurs at odddenominator fillings and can be understood in terms of weakly interacting composite fermions, which are bound states of electrons and vortices. In the second LL (SLL), FQHE has been observed at evendenominator fillings such as 5/2 and 2+3/8 and a description of these states lies beyond the purview of noninteracting composite fermions. In this talk, I will demonstrate that these states can be understood using the "parton" theory which generalizes the idea of composite fermion. In particular, I will elucidate our recent work on the parton construction of wave functions to describe nonAbelian paired states that potentially capture the underlying physical mechanism for the FQHE observed in the SLL [1,2], at 1/4 in wide quantum wells of GaAs [3] and at 1/2 in the third LL of monolayer graphene [4]. More generally, our work suggests that the parton theory provides a unified description of the quantum Hall effects [5]. 
Tuesday, March 15, 2022 1:54PM  2:30PM 
G45.00005: A novel method distinguishing between topological orders Invited Speaker: Mordehai (Moty) Heiblum Nonabelian anyons are prospective candidates for faulttolerant topological quantum computation due to their longrange entanglement. The =5/2 quantum Hall state has been long proposed to host nonabelian quasiparticles. The gapless edge modes can mirror the topological order of the state, resting on ‘bulkedge’ correspondence. Supporting an odd number of Majorana (neutral) modes guarantees the nonabelian nature of the state. Recent measurements of the state’s thermal conductance, with =p^{2}k_{B}^{2}/3h, provided solid evidence for the nonabelian ParticleHole Pfaffian (PHPf) topological order. Numerical calculations, however, favor the Pfaffian (Pf) and antiPfaffian (APf) orders. Since the =5/2 state hosts integer, fractional, and neutral modes, it was suggested that lack of thermal equilibration among the different edge modes of the APf order could account for the apparent PHPf order. 
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