Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session F07: Fractional Quantum Hall 2 
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Sponsoring Units: DCMP Chair: Jeanie Lau, Ohio State University Room: LACC 153B 
Tuesday, March 6, 2018 11:15AM  11:27AM 
F07.00001: Statistical particlehole symmetry and the quantized Hall state at ν=5/2 Chong Wang, Ashvin Vishwanath, Bertrand Halperin In the absence of Landau level mixing, the halffilled Landau level possesses particlehole symmetry which is spontaneously broken by the Pfaffian/antiPfaffian topological orders, which appear to be favored in numerical studies of the ν=5/2 quantum Hall state. Here we investigate the effect of quenched disorder on the nature of the ν=5/2 fractional quantum Hall state and compare our results with recent experimental measurement of thermal Hall effect at ν=5/2. 
Tuesday, March 6, 2018 11:27AM  11:39AM 
F07.00002: In Search of the Dirac Cone in the HalffilledLandauLevel CompositeFermion Liquid Frederick D Haldane, Jie Wang The "web of duality" supports D. Son's Dirac picture of the composite fermion (CF) Fermi liquid state of a halffilled 2D Landau level, which implies that an analog of the "Dirac cone" state should describe a CFL state with a single empty "CF orbital" at the center of the "Fermi sea". WIth an inversionsymmetric Fermi surface, this implies that the "Dirac cone" k=0 quasihole state is an inversionsymmetric zeromomentum state with an even number of particles. With particlehole symmetry, such states have an extra twofold degeneracy. Model CFL states based on the HalperinLeeRead picture are remarkably close to having a generalized particlehole (with inversion) symmetry but as a quasihole is moved inside the Fermi surface this breaks down: the two particlehole conjugate states become orthogonal as the quasihole reaches the Fermi sea center k=0. By forming the two orthogonal linear combinations that diagonalize the overlap matrix, two branches of singlequasihole excitations strongly reminiscent of the (electron) hole and positron states of an electronrich "Dirac sea" are obtained. As the quasihole k approaches k_{F}, the model states have large overlap with numerical exact eigenstates of the Coulomb interaction. 
Tuesday, March 6, 2018 11:39AM  11:51AM 
F07.00003: Berry Phase in CompositeFermiLiquid States Jie Wang, Scott Geraedts, Edward Rezayi, Frederick D Haldane The CompositeFermiLiquid (CFL) state is a gapless state that can occur at Landaulevel filling 1/m when m is even, and an emergent Fermi surface for composite fermions forms. We examine the Berry phase associated with moving one composite fermion around different closed paths near the Fermi surface, using a model wavefunction parameterized by “compositefermion occupation patterns” that explicitly has a Fermi surface. When these patterns correspond to weakly excited Fermi Sea, they are very accurate approximation for the exact Coulombinteraction ground states, allowing exact states to be identified with compositefermion configurations. A manybody analog of the kspace Berry phase is defined and examined both from exact states by exact diagonization and from comparison with model wavefunctions by the recently proposed lattice Monte Carlo method [arXiv: 1710.09729]. We also comment on the origin of the Dirac cone, and the onequarterfilled state which is not particlehole symmetric. 
Tuesday, March 6, 2018 11:51AM  12:03PM 
F07.00004: Imaging anyons with scanning tunneling microscopy Zlatko Papic, Roger Mong, Ali Yazdani, Michael Zaletel NonAbelian anyons have long been predicted to occur in the fractional quantum Hall (FQH) phases that form in twodimensional electron gases in the presence of a large magnetic field. However, direct experimental evidence of anyons and tests that can distinguish between Abelian and nonAbelian quantum ground states with such excitations have remained ambiguous. Here we propose a new experimental approach to directly visualize the structure of interacting electronic states of FQH phases with the scanning tunneling microscope (STM). Our theoretical calculations show how spectroscopy mapping with the STM near individual impurity defects can be used to image fractional statistics in FQH states, identifying unique signatures that can distinguish different quantum Hall phases. In this talk, I'll talk about the theoretical signatures of Laughlin, MooreRead and Hierarchy states. 
Tuesday, March 6, 2018 12:03PM  12:15PM 
F07.00005: Search for genons in fractional Chern insulator states on an infinite cylinder Matteo Ippoliti, Michael Zaletel

Tuesday, March 6, 2018 12:15PM  12:27PM 
F07.00006: Fractional Quantum Hall effect in Ultrahigh Quality Fewlayer Black Phosphorus Transistors Jiawei Yang, Son Tran, Shi Che, Takashi Taniguchi, Kenji Watanabe, Hongwoo Baek, Dmitry Smirnov, Ruoyu Chen, Chun Ning Lau Black phosphorus(BP), as the only noncarbon elemental layered allotrope, has been investigated intensively because of its possession of high mobility and tunable gap. Here we report the fabrication of fewlayer BP field effect transistor with mobility up to 55,000 cm^{2}/Vs, and observation of two fractional QH states at filling factors n ~ 4/3 and 0.56 ± 0.1, underscoring BP as a tunable 2D platform for exploring electron interactions. 
Tuesday, March 6, 2018 12:27PM  12:39PM 
F07.00007: Observation of Fractional Quantum Hall Effect in an InAs Quantum Well Meng Ma, Md. Shafayat Hossain, Kevin Villegas Rosales, Hao Deng, Thomas Tschirky, Werner Wegscheider, Mansour Shayegan The InAs twodimensional electron system is one of the prime candidates for hosting exotic quasiparticles such as Majorana fermions and parafermions that exhibit nonAbelian statistics. To fulfill its full promise, however, the system must be clean enough to show evidence of electronelectron interaction. Here we study a very low disorder, 24nmwide InAs quantum well with density of 7.8 × 10^{11} cm^{2} and lowtemperature mobility 1.8 × 10^{6} cm^{2}/Vs. The sample exhibits resolvable Shubnikov de Haas oscillations at magnetic field as low as ≈ 0.5 T (v = 68) and becomes spinresolved at B > 0.9 T (v ≤ 37). At a temperature of ≈ 35 mK and B ≈ 24 T, we observe a deep minimum in longitudinal resistance, accompanied by a nearly quantized Hall plateau at filling factor v = 4/3. This observation places the InAs twodimensional electron system among the few systems that exhibit fractional quantum Hall effect, and it is an important step towards the realization of exotic quasiparticles, such as parafermions, that are required for universal quantum computation. 
Tuesday, March 6, 2018 12:39PM  12:51PM 
F07.00008: Wide AlAs quantum wells with > 10^{6} cm^{2}V^{1}s^{1} mobility Edwin Chung, K Baldwin, K West, Mansour Shayegan, Loren Pfeiffer Modulationdoped Al_{0.33}Ga_{0.67}As/AlAs/Al_{0.33}Ga_{0.67}As quantum wells with electron densities of 1.4, 2.2, and 3.3 x 10^{11} cm^{2} were grown with well widths ranging from 11 nm to 50 nm. In these samples electrons occupy inplane valleys with large and anisotropic effective masses (longitudinal and transverse effective masses are 1.0 and 0.21, in units of free electron mass). We find that the optimized well width varies according to sample density, most likely because of scattering contributions from the second subband. Our highest quality samples show exceptional mobility values as high as 2.4 x 10^{6} cm^{2}V^{1}s^{1 }at the density of 2.2 x 10^{11} cm^{2}, and we observe high order fractional quantum Hall states up to 8/15 in samples with 1.4 x 10^{11} cm^{2 }density. These advances clearly demonstrate that 2D electrons in AlAs now have quality comparable to modern GaAs, highlighting the system as an excellent candidate to study electronelectron interactions in an anisotropic, multivalley environment. 
Tuesday, March 6, 2018 12:51PM  1:03PM 
F07.00009: Pairing of single electron additions at the edge of an ultraclean mini 2DEG Ahmet Demir, Neal Staley, Spencer Tomarken, Loren Pfeiffer, K West, Raymond Ashoori We have created laterally large, quantum well based, quantum dots in a system with no unscreened dopants. Using singleelectron capacitance spectroscopy (SECS) in a dilution refrigerator, we can identify the capacitance peak for the addition of the first electron to a dot and record subsequent capacitance peaks in the addition spectrum up to dot occupancies of thousands of electrons. SECS records the electron addition energies and the tunneling density of states within a dot as a function of magnetic field and energy. Previous measurements showed well defined transitions into integer quantum Hall states in these spectra. To investigate fractional states, we produced this new, cleaner, device with a larger physical size so that the dot would behave as a small 2D electron system. Here we report the observation in the addition spectra of individually localized states, extended states, incompressible Landau gaps, and pairing of single electron additions between nu=2 and nu=3. We observe the pairing over similar filling factor ranges where interferometry experiments display pairing effects as in Choi et al. Nat. Comm. 6, 7435 (2015) 
Tuesday, March 6, 2018 1:03PM  1:15PM 
F07.00010: Probing spin polarization of quantum Hall states by tunneling into a quantum Hall ferromagnet. Heun Mo Yoo, Joonho Jang, Loren Pfeiffer, K West, Raymond Ashoori

Tuesday, March 6, 2018 1:15PM  1:27PM 
F07.00011: Fractional Quantum Hall Effect in AlAs 2D Electrons Kevin Villegas Rosales, Edwin Chung, Hao Deng, K Baldwin, K West, Loren Pfeiffer, Mansour Shayegan We study twodimensional (2D) electrons confined to an AlAs quantum well, with density n = 1.5 x 10^{11} cm^{2} and unprecedented high mobility, 10^{6} cm^{2}V^{1}s^{1}. The 2D electrons in this system occupy conductionband minima (valleys) with anisotropic dispersion and effective mass. The magnetoresistance traces exhibit a rich sequence of fractional quantum Hall states near filling factor ν = ½, up to highorder fractions 8/15 and 8/17. We study the temperature dependence of these states, and extract energy gaps and composite fermion effective masses. We compare these with the relevant parameters in other 2D systems such as 2D electrons confined to GaAs quantum wells. 
Tuesday, March 6, 2018 1:27PM  1:39PM 
F07.00012: Superuniversality of Quantum Hall Interplateaux Transitions and SL(2,Z) Modular Transformations Aaron Hui, Michael Mulligan, EunAh Kim The theoretical understanding of “superuniversality,” [1] the phenomenon where all quantum Hall (QH) plateaux transitions exhibit the same correlation length and dynamical critical exponents, is a longstanding challenge. Although the correspondence rule of Ref. [2] says that superuniversality should arise at critical points between plateaux related by the addition of Landau levels, a particlehole transformation, or flux attachment, it is not clear how such insensitivity would be realized theoretically. Here we introduce a new effective description with an emergent U(N) gauge symmetry for a transition between an integer QH state and an insulator. We then use SL(2,Z) transformations, which formally implement the transformations in Ref. [2], to generate descriptions for a large class of QH transitions. In the t' Hooft large N limit, the correlation length and dynamical critical exponents are the same at all such transitions in the absence of disorder. We argue that this conclusion survives away from the large N limit using recent duality conjectures, thereby providing theoretical support for the observed superuniversality. 
Tuesday, March 6, 2018 1:39PM  1:51PM 
F07.00013: Composite Fermions on a Torus Songyang Pu, Yinghai Wu, Jainendra Jain We report on an explicit construction of the composite fermion (CF) wave functions in the lowest Landau level in the torus geometry using a modified JainKamillatype projection method. [1] Our construction produces valid wave functions for a large class of ground and excited state configurations of composite fermions for arbitrary filling factors, and allows theoretical study of large systems of composite fermions on a torus. A direct comparison with exact eigenfunctions and eigenenergies known for small systems has shown that our wave functions are extremely accurate representations of the Coulomb eigenstates. We have also extended our construction to the CF Fermi sea, and compared our results with other wave functions for the CF Fermi sea in the literature. 
Tuesday, March 6, 2018 1:51PM  2:03PM 
F07.00014: Dependence of Electron Temperature on the Incident Microwave Power in the PhotoExcited GaAs/AlGaAs 2D Electron System Tharanga Nanayakkara, Rasanga Samaraweera, Binuka Gunawardana, C. Rasadi Munasinghe, Annika Kriisa, Christian Reichl, Werner Wegscheider, Ramesh Mani We examined the influence of microwave radiation on both amplitude of Shubnikovde Haas (SdH) oscillations and null magnetic field longitudinal magnetoresistance at low temperatures, T<4.2 K, in GaAs/AlGaAs Hall bar devices. SdH oscillations have been analyzed over the parameter space given by 2.3<ω_{c}/ω<5.2, where ω_{c}=eB/m*, ω=2πf, B is the magnetic field, m* is the effective mass and f is the microwave frequency. Microwave radiation over the frequency range 30≤f≤100 GHz with peak source power 1≤P≤10 mW served to photoexcite a high mobility (10^{7}cm^{2}/Vs). 2D electron system (2DES) as magnetoresistance traces were obtained as a function of the microwave power P and T. Then, fits of the SdH oscillations line shape served to extract the electron temperature (T_{e}) as a function of P and T over the abovementioned parameter window. Theory has proposed that, in the ω_{c}/ω≥1 regime, both the electron temperature and radiation energy absorption rate (S_{p}) exhibit relatively constant response, while in ω_{c}/ω≤1 regime, both T_{e} and S_{p} exhibit oscillatory behavior. We compare the results of this experimental study with the theoretical predictions and correlate the T_{e }and P. 
Tuesday, March 6, 2018 2:03PM  2:15PM 
F07.00015: Study of current bias induced carrier heating effect in the regime of Shubnikov de Haas oscillations in high mobility GaAs/Al_{x}GaAs_{1x }twodimensional electron system Chathuranga Munasinghe, Binuka Gunawardana, R.L. Samaraweera, Tharanga Nanayakkara, Zhuo Wang, Annika Kriisa, U. Kushan Wijewardena, Christian Reichl, Werner Wegscheider, Ramesh Mani In a current carrying metallic system, temperature of the carriers depends on Joule heating and energy relaxation through electron diffusion or electronphonon coupling [01, 02, 03]. In this study, carrier heating induced by ac bias current in high mobility GaAs/Al_{x}GaAs_{1x }twodimensional electron system at temperature range of 1.6 ≤ T ≤ 4.2 K was investigated using alteration in the line shape of Shubnikov de Haas oscillations. Haas oscillation was analyzed, and fit base on LifshitzKosevich theory and extracted carrier temperatures indicate that the electron diffusion predominant in the energy relaxation process of the system and the 2DES is in a quasiequilibrium state where the hot electron situation is attained. 
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