Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session S01: Fractional Quantum Hall Effect: Novel States and ExcitationsFocus

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Sponsoring Units: DCMP Chair: Lucia Steinke, Texas A&M University Room: BCEC 106 
Thursday, March 7, 2019 11:15AM  11:27AM 
S01.00001: Zero modes, Bosonization and Topological Quantum Order: Composite Fermions in Second Quantization Li Chen, Sumanta Bandyopadhyay, Kun Yang, Alexander Seidel We develop recursion relations, in particle number, for all (unprojected) Jain composite fermion (CF) wavefunctions. 
Thursday, March 7, 2019 11:27AM  11:39AM 
S01.00002: Variational principle for an incompressible fluid with Hall viscosity and gapless surface modes Gustavo M Monteiro, Alexandre Abanov Hydrodynamics is a powerful tool to study strongly interacting systems, including for example the fractional quantum Hall effect (FQHE). The main features of the quantum Hall hydrodynamics are the incompressibility of the electron flow, due to the gap separation between the FQH ground state and the excited states, and the relation between the density of the fluid and its vorticity. Motivated by this example, we focus in this work on the variational and Hamiltonian formulations of incompressible twodimensional fluid dynamics with free surface and nonvanishing Hall viscosity. We show that within the variational principle the Hall viscosity contribution corresponds to a purely geometric boundary term. This term modifies effective boundary conditions on the free surface. The modified boundary conditions have a interpretation describing an additional pressure at the free surface proportional to the angular velocity of the surface itself. These boundary conditions are believed to be universal since the proposed hydrodynamic action is fully determined by the symmetries of the system. The extension of this variational principle to compressible flows will be also considered in this talk. 
Thursday, March 7, 2019 11:39AM  11:51AM 
S01.00003: Geometric quench in the fractional quantum Hall effect: exact solution in quantum Hall matrix models and comparison with bimetric theory Matthew Lapa, Andrey Gromov, Taylor Hughes We investigate the recently introduced geometric quench protocol for fractional quantum Hall (FQH) states within the framework of exactly solvable quantum Hall matrix models. In the geometric quench protocol a FQH state is subjected to a sudden change in the ambient geometry, which introduces anisotropy into the system. We formulate this quench in the matrix models and then we solve exactly for the postquench dynamics of the system and the quantum fidelity (Loschmidt echo) of the postquench state. Next, we explain how to define a spin2 collective variable g_{ab}(t) in the matrix models, and we show that for a weak quench (small anisotropy) the dynamics of g_{ab}(t) agrees with the dynamics of the intrinsic metric governed by the recently discussed bimetric theory of FQH states. We also find a modification of the bimetric theory such that the predictions of the modified bimetric theory agree with those of the matrix model for arbitrarily strong quenches. 
Thursday, March 7, 2019 11:51AM  12:03PM 
S01.00004: Interlayer fractional quantum Hall effect in a coupled graphene doublelayer Xiaomeng Liu, Zeyu Hao, Kenji Watanabe, Takashi Taniguchi, Bertrand I. Halperin, Philip Kim In twodimensional (2D) electron systems under strong magnetic fields, interactions can cause fractional quantum Hall (FQH) effects. Bringing two 2D conductors to proximity, a new set of correlated states can emerge due to interactions between electrons in the same and opposite layers. Here we report interlayer correlated FQH states in a system of two parallel graphene layers separated by a thin insulator. Current flow in one layer generates different quantized Hall signals in the two layers. This result is interpreted by composite fermion (CF) theory with different intralayer and interlayer ChernSimons gaugefield coupling. We observe FQH states corresponding to integer values of CF Landau level (LL) filling in both layers, as well as "semiquantized" states, where a full CF LL couples to a continuously varying partially filled CF LL. Remarkably, we also recognize a quantized state between two coupled halffilled CF LLs, attributable to an interlayer CF exciton condensate. 
Thursday, March 7, 2019 12:03PM  12:15PM 
S01.00005: Microwave photoexcited transport in the GaAs/AlGaAs 2DES Annika Kriisa, Christian Reichl, Werner Wegscheider, Ramesh Mani Collective bulk plasmon excitations of a two dimensional electronic system (2DES) evolve into magnetoplasmons in the presence of a perpendicular magnetic field, with a low frequency cutoff determined by the dispersion relation ω_{MP} = (ω_{C}^{2} + ω_{P}^{2})^{1/2}, where the plasmon frequency ω_{P}^{2} = (ne^{2} /2ε_{eff}ε_{o}m*)k, with k the plasmon wave vector, and ω_{c} the cyclotron resonance frequency. Studies of narrow Hall bar type GaAs/AlGaAs specimens of width, w, have long ago suggested that localization of the plasmon within the boundaries of the sample can lead to the wave vector selection k = π/w and the observation of the corresponding resonance in magnetotransport under photoexcitation. The observation of zeroresistance states and associated radiation induced magnetoresistance oscillations under microwave/mmwave/terahertz photoexcitation has brought new interest in the role of the magnetoplasmon, if any, in the ultra high mobility GaAs/AlGaAs 2DES and its interaction with this photoexcited transport phenomena mentioned above. In this study, we reexamine through experiment the role of the magnetoplasmon in the GaAs/AlGaAs magnetotransport and report the results. 
Thursday, March 7, 2019 12:15PM  12:27PM 
S01.00006: WITHDRAWN ABSTRACT

Thursday, March 7, 2019 12:27PM  12:39PM 
S01.00007: Pairing and Pair Tunneling of Electrons at the Edge of a GaAs Quantum Dot TwoDimensional Electronic System Ahmet Demir, Neal Staley, K. W. Baldwin, Kenneth West, Loren Pfeiffer, Raymond Ashoori We have large (diameter ~0.8 μm) ultraclean quantum dots that act as mini2D electron systems and studied their single electron addition spectra at ~45 mK using capacitive sensing. Single electrons tunnel from an n+ GaAs electrode across an AlGaAs tunnel barrier into an otherwise electrically floating quantum dot. We measured the magnetic field dependence of electron addition energies from a completely empty dot, up to dot occupancies of ~2000 electrons. Here, we report the observation in the addition spectra of individually localized states, incompressible Landau gaps, and isolated tunneling to edge states. We see electron additions to the edge states between filling factors ν = 1 and ν = 2 with single flux quantum (h/e) periodicity in magnetic field. Remarkably, between filling factors ν = 2 and ν = 5, we observe the pairing of electron additions to states at the edges of the quantum dots with a corresponding 2e charge tunneling and with (h/2e) periodicity in magnetic field. These results are consistent with interferometry work from the group of Heiblum[1] showing an unexpected h/2e periodicity around the same filling factors, and they suggest that the same correlated electron physics is creates a novel pair tunneling effect. 
Thursday, March 7, 2019 12:39PM  12:51PM 
S01.00008: Study of spin splitting of Shubnikov de Hass oscillations under microwave photoexcitation in the GaAs/AlGaAs 2DES Tharanga Nanayakkara, Rasanga Samaraweera, Binuka Gunawardana, C. Rasadi Munasinghe, U. Kushan Wijewardena, Sajith Withanage, Annika Kriisa, Ramesh Mani, Christian Reichl, Werner Wegscheider We perform magneto transport measurements on GaAs/AlGaAs 2D electron system to understand the influence of the microwave photoexcitation on the spin splitting of the Shubnikovde Haas oscillations at liquid helium temperatures. The aim of the study is to determine the magnitude of the electron heating under microwave photoexcitation by examining observable spin splitting and variation thereof under photoexcitation at high filling factors. Thus, we apply a LifshitzKosevevich^{1} type formula to describe the magneto transport data and report here the relevant results. 
Thursday, March 7, 2019 12:51PM  1:03PM 
S01.00009: Collective excitations in the MooreRead phase: view from superspace Andrey Gromov, Shinsei Ryu, Emil J Martinec We present a microscopic theory of the neutral collective modes supported by the MooreRead fractional quantum Hall state. The theory is formulated in terms of the trial states describing the GirvinMacDonaldPlatzman (GMP) mode and its fermionic counterpart, known as the "Neutral Fermion" mode. To access both modes simultaneously the MooreRead state is first lifted to the superspace. These modes are created by the same operator which acts in the superspace. The Grassman variables are auxilliary and are integrated over in the end. 
Thursday, March 7, 2019 1:03PM  1:15PM 
S01.00010: Oneplaquette Chern number: Manybody Chern number without integration Koji Kudo, Haruki Watanabe, Toshikaze Kariyado, Yasuhiro Hatsugai The NiuThoulessWu formula defines the manybody version of the Chern number that characterizes the quantized Hall conductance in the presence of disorders or interactions. In this talk, we provide numerical evidence that the integration by twisted angles in the NiuThoulessWu formula is unnecessary if the system size and the excitation gap are sufficiently large. The Berry curvature itself is effectively quantized and the error decays exponentially with the system size. The lack of integration reduces the computational cost, which is advantageous in the interacting manybody problems for a sufficiently large system size. We also discuss the accuracy of the effective quantization in the vicinity of quantum phase transitions. 
Thursday, March 7, 2019 1:15PM  1:27PM 
S01.00011: Search for exact local Hamiltonians for general fractional quantum Hall states Sreejith Ganesh Jaya, Mikael Fremling, Gun Sang Jeon, Jainendra Jain We report on our systematic attempts at finding local interactions for which the lowestLandaulevel projected compositefermion wave functions are the unique zero energy ground states. We study in detail the simplest nontrivial system beyond the Laughlin states, namely bosons at filling factor 2/3 and identify local constraints among clusters of particles in the ground state. By explicit calculation, we show that no Hamiltonian up to (and including) four particle interactions produces this state as the exact ground state, and speculate that this remains true even when interaction terms involving greater number of particles are included. Surprisingly, we can identify an interaction, which imposes an energetic penalty for a specific entangled configuration of four particles with relative angular momentum of 6, that produces a unique zero energy solution (as we have confirmed for up to 12 particles). This state is not identical to the projected CF state, but have high overlaps with the CF state and the same root partition, quasiparticle and neutral excitation spectrum as the CF state. On the quasihole side, the quantum numbers of the low energy states agree with the CF state but these states are not separated from the others by a clearly identifiable gap. 
Thursday, March 7, 2019 1:27PM  1:39PM 
S01.00012: Prediction of a new nonAbelian state at ν = 1/4 in Wide Quantum Wells* William Faugno, Ajit Coimbatore Balram, Maissam Barkeshli, Jainendra Jain For zero width systems, the ground state at filling factor ¼ is described by the fully polarized composite fermion Fermi sea. However, fractional quantum Hall effect (FQHE) has been observed at ¼ in wide quantum well samples [1]. We consider several singlecomponent candidate states, and conclude that the nonAbelian “22111parton” state is the most likely candidate. Our calculated phase diagram as a function of the quantum well width and the density is in very good agreement with experiments. We suggest further experiments that can confirm the nature of the ¼ state and, in particular, distinguish it from other candidate states. We also consider a bilayer system at total filling ¼ as a function of the interlayer separation and predict that it does not support any incompressible FQHE state. 
Thursday, March 7, 2019 1:39PM  1:51PM 
S01.00013: Stripe Pairing Order in the 5/2filling Fractional Quantum Hall State Luiz Santos, Yuxuan Wang, Eduardo Hector Fradkin The nu=5/2 fractional quantum Hall (FQH) state can be effectively described by a paired state of composite fermions with a chiral pwave order parameter. Motivated by recent works showing an instability of this FQH state towards a phase with broken rotation symmetry, we study the properties of a pwave pair density wave (PDW) state. We show that the domain walls (DWs) of the PDW order parameter support a pair of counterpropagating Majorana modes whose properties depend on the competition between the Fermi energy and the strength of the PDW order parameter. At weak coupling, the hybridization of DWs generically gives rise to a Majorana Fermi surface (MFS) that is protected by inversion and particlehole symmetries. A uniform pwave component gaps the MFS causing the system to enter a striped nonAbelian state with a chiral edge Majorana. At strong coupling, on the other hand, the system is described by a gapped phase without chiral Majorana edge states, which we identify with an striped Abelian paired state. The striped paired FQH state is therefore a fertile arena to study transitions between different topological orders tunned by the strength of the PDW order parameter. 
Thursday, March 7, 2019 1:51PM  2:03PM 
S01.00014: Composite fermions mass in an anisotropic twodimensional electron system Kevin Villegas Rosales, Edwin Chung, Hao Deng, Kenneth West, K. W. Baldwin, Loren Pfeiffer, Mansour Shayegan Recent advances in molecular beam epitaxy capabilities have stablished a new record in the quality of AlAs twodimensional electron systems (2DESs). This breakthrough allows us to study the temperature dependence of fractional quantum Hall states up to ν = 7/15 and 7/13 in the extreme quantum limit. We report on the energy gaps and Shubnikovde Haas mass (m_{CF}) of composite fermions in samples with density n = 1.04 x 10^{11} cm^{2} and quantum well widths of 35 and 50 nm. The measured m_{CF} are 0.68 and 1.2 (in units of free electron mass) for the 35 and 50 nm wide quantum well near ν = ½, respectively. We contrast our results with the previously reported energy gaps and m_{CF} of 2DESs in GaAs and ZnO, and the 2D hole system in GaAs. Our experiments on AlAs 2DESs demonstrate the important role of electron layer thickness in determining the energy gaps and m_{CF}. 
Thursday, March 7, 2019 2:03PM  2:15PM 
S01.00015: Parton states as unique ground states of frustration free quantum Hall Hamiltonians with Fibonacci anyon excitations Mostafa Tanhayi Ahari, Sumanta Bandyopadhyay, Zohar Nussinov, Alexander Seidel, Gerardo Ortiz We develop a general formalism to systematically derive frustrationfree fractional quantum Hall (FQH) Hamiltonians in the presence of Landau level (LL) mixing. Their ground state correlations organize according to entangled Pauli principles, encoding the fluid’s DNA and, dictating the fractional nature of the statistics of their topological excitations. As we will show, the densest ground state  conjectured to be an incompressible quantum liquid  can be uniquely associated to a certain (closedshell) parton state. Using Sduality, we show that for the case of 4 LLs, excitations of a filling fraction 2/3 liquid admit nonAbelian statistics and correspond to Fibonacci anyons. 
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