Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session D66: Unconventional States and Excitations in the Fractional Quantum Hall EffectInvited
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Sponsoring Units: DCMP Chair: Steven Kivelson, Stanford Univ Room: Four Seasons 1 |
Monday, March 2, 2020 2:30PM - 3:06PM |
D66.00001: Precursors to Exciton Condensation in Quantum Hall Bilayers Invited Speaker: James Eisenstein Bilayer two-dimensional electron systems at high magnetic field exhibit an interlayer coherent excitonic phase when the layer separation is sufficiently small, the temperature sufficiently low, and the total electron density in the bilayer equals the degeneracy of a single Landau level. This phase is well known to display exotic transport phenomena, notably Josephson-like interlayer tunneling and essentially dissipationless transport of excitons across the bulk of the 2D system. While first detected twenty years ago in GaAs-based double quantum wells, this and related interlayer correlated phases have recently been observed in graphene-based multilayer systems. |
Monday, March 2, 2020 3:06PM - 3:42PM |
D66.00002: Parton theory of the fractional quantum Hall effect: New developments Invited Speaker: Jainendra Jain In the parton construction [1], one divides each electron into fictitious particles called partons, places each species of partons into an IQH state, and then fuses the partons back into physical electrons. This produces candidate FQHE states that are products of IQH states. Some of the states so produced are predicted to have non-Abelian excitations [2]. I will review recent work on the applicability of such wave functions to physically observed states at ν=5/2 [3], ν=2+6/13 [4], and ν=1/4 in wide quantum wells [5]. Theory suggests that a non-Abelian "221" state may appear at ν=1/2 in bilayer and trilayer graphene [6]. I will also discuss exact Hamiltonians for a subclass of such states [6,7]. |
Monday, March 2, 2020 3:42PM - 4:18PM |
D66.00003: Duality in Quantum Hall Compressible States Invited Speaker: Eduardo Fradkin It has long been known (at least since 1997) mpirically that quantum Hall plateau transitions enjoy an apparent self-dualty symmetry. The emaning of this statement is that the current-voltage (I-V) curves are non-linear and are symmetric around their liner behavior at the quantum phase transition. This behavior was first observed in dirtier samples and is now know to occur in the compressible sattes at filling fractions 1/2 and 1/4. This empirical result was interpreted by Shimshoni, Sondhi and Shahar (PRB 55, 13730 91997)) as a manifestation of a particle-vortex duality.Yet, the origin of this symmetry has been misterious and has remained unexplained until quite recently. In a very recent paper (Hart Goldman and Eduardo Fradkin, PRB 98, 165137 (2018)) Goldman and myself used the recently developed dualities of Dirac fermions (D. T. Son Phys. Rev X. 5, 031027 (2015); N. Seiberg, T. Senthil, C. Wang and E. Witten, Ann. Phys. 374, 3095 (2016)) to show that the mirror symmetry of the Jain sequences converging on 1/2n compressible states explain the observed self-duality as a property of the compressible states. Hart Goldman was the lead author of this work. |
Monday, March 2, 2020 4:18PM - 4:54PM |
D66.00004: New unconventional plasmons in the N=1 Landau level Invited Speaker: Lingjie Du In the partially filled second Landau level (SLL) emergent exotic quantum fluids overlap and interplay with fractional quantum Hall (FQH) liquids. Collective modes of the exotic quantum fluids uncover underlying physical mechanisms responsible for emerging new ground states [1-3]. Resonant inelastic light scattering (RILS) spectra access unprecedented collective modes in the FQH regime of the SLL: intra-Landau-level plasmons[3]. The plasmons herald rotational-symmetry-breaking (nematic) phases in the SLL and reveal the nature of long-range translational invariance in these phases. The intricate dependence of plasmon features on filling factor provides new insights on complex interplay between topological quantum Hall order and nematic electronic liquid crystal phases. A marked intensity minimum in the plasmon spectrum at Landau level filling factor v = 5/2 strongly suggests that the paired state, which may support non-Abelian excitations, overwhelms competing phases, revealing the robustness of the 5/2 superfluid state for small tilt angles. In contrast, a sharp and intense plasmon peak in the state at v=7/3 reveals that the macroscopic coherence of the FQH liquid coexists with nematic order, supporting the proposed model of a FQH nematic at 7/3. Other interpretations of the new collective mode, such as chiral graviton [4], will be discussed. |
Monday, March 2, 2020 4:54PM - 5:30PM |
D66.00005: Composite Fermions near Half-filled Landau Levels: Precise Experimental Tests of Luttinger Theorem, Particle-Hole Symmetry, and Fermi Sea Anisotropy Invited Speaker: Mansour Shayegan Composite fermions (CFs), exotic particles formed by pairing an even number of flux quanta to each electron, |
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