Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session B45: FQHE: Fractional Statistics and Other DevelopmentsInvited Live Streamed

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Sponsoring Units: DCMP Chair: Smitha Vishveshwara, University of Illinois at UrbanaChampaign Room: McCormick Place W375D 
Monday, March 14, 2022 11:30AM  12:06PM 
B45.00001: Direct observation of anyonic braiding statistics at theν=1/3 fractional quantum Hall state Invited Speaker: James R Nakamura Anyons are exotic quasiparticles which exhibit fractional braiding statistics. We report experimental evidence for anyonic braiding statistics at the ν = 1/3 fractional quantum Hall state in a FabryPerot interferometer fabricated on a GaAs/AlGaAs heterostructure. The structure incorporates screening wells to suppress Coulomb charging effects, enabling the possibility of observing the anyonic phase without confounding by bulkedge interaction. We observe AharonovBohm interference with discrete jumps in phase consistent with anyonic phase θ = 2π/3. 
Monday, March 14, 2022 12:06PM  12:42PM 
B45.00002: Fractional statistics in anyon collisions Invited Speaker: Gwendal Feve Two dimensional systems can host exotic quasiparticles, called anyons, which obey intermediate quantum statistics between fermions and bosons characterized by a phase φ varying between 0 and π [1,2]. As an example, in the fractional quantum Hall regime, obtained by applying a strong magnetic field perpendicular to a twodimensional electron gas, elementary excitations carry a fractional charge [3,4] and obey fractional statistics [1,2] with an exchange phase φ=π/m (where m is an odd integer) for Laughlin states corresponding to a fractional filling υ=1/m of the first Landau level. 
Monday, March 14, 2022 12:42PM  1:18PM 
B45.00003: An exactly solvable model of strongly interacting fermions in a magnetic field Invited Speaker: Sreejith Ganesh Jaya The lowest Landau level fractional quantum Hall (LLLFQH) states are well understood as integer quantum Hall (IQH) states of weakly interacting composite fermions occupying Landau levels in an effective magnetic field. Their wavefunctions closely approximate the Coulomb eigenstates but in general are not exact eigenstates of any known local Hamiltonians [1]. We present a model Hamiltonian for strongly interacting spinpolarized fermions of filling fractions less than 1/2 in the limit where the interaction is strong compared to the cyclotron energy [2]. The Hamiltonian produces the same low energy quantum numbers as the composite fermions wavefunctions describing LLLFQH states while allowing exact formal solutions to ground states, quasihole, quasiparticle and neutral excitations at arbitrary filling fractions of the form n/(2pn+1). We present results in the spherical, torus and cylindrical geometries to demonstrate the onetoone correspondence with the non interacting fermion model in an effective magnetic field. We also show numerical results from exact diagonalization, Monte Carlo and iDMRG studies testing the adiabatic connection with Coulomb physics, quasiparticle Berry phase and charge [3]. 
Monday, March 14, 2022 1:18PM  1:54PM 
B45.00004: Composite fermion liquid at Landau level filling factor 1/2: Bloch ferromagnetism, Luttinger theorem, and particlehole symmetry Invited Speaker: Md. Shafayat Hossain The ground state of a dilute, twodimensional electron system has been a topic of intense theoretical and experimental speculation, because the physics here is governed by strong correlations. Back in 1929, Felix Bloch proposed a fully spinpolarized ground state for a lowdensity fermionic system which is historically the first predicted quantum manybody phase. However, this state eluded experimental realization for the last nine decades. In the first part of my talk, I will present an experimental realization of the elusive interactiondriven spin polarization in a system of unusual suspects, namely composite fermions (CFs). CFs are quasiparticles, each composed of an electron and two flux quanta, formed in the halffilled Landau level of a twodimensional electron system. As the density of CFs is lowered, the CFs become strongly interacting and make a sudden transition into a ferromagnetic state, which we probe directly via measuring the CF Fermi sea [1]. In the second part, I will discuss the nature of the CF Fermi sea in the presence of strong CFCF interaction. In particular, the applicability of the Luttinger theorem for the Fermi sea area and particlehole symmetry will be highlighted [2]. 
Monday, March 14, 2022 1:54PM  2:30PM 
B45.00005: Raman scattering and excitations in fractional quantum Hall systems Invited Speaker: Dam T Son Raman scattering provides an important probe of the fractional quantum Hall effect. In addition to the enegy spectrum of magnetoroton exciitations, polarized Raman scattering can also measure the spin of the magnetoroton. The problem of Raman scattering involves physics at two vastly different scales: the scale of the energy of the photons and the energy scale of the FQHE. In a certain regime, one can "factor out" the calculable physics at the photon energy scale, reducing the problem to the calculation of the spectral density of a pair of spin2 operators on a single Landau level. Thus Raman scattering does not measure the density response but a certain "stress response." This is reminiscent of Haldane's proposal that the longwavelength magnetoroton is a kind of "emergent graviton." We will argue that the single mode approximation does not work for Jain states near ν=1/4. In the simplest scenario these states contain two magnetoroton modes, which have different chirality for ν=n/(4n1) and the same chirality for ν=n/(4n+1), measureable in polarized Raman scattering. Polarized Raman scattering, in principle, can also help the determination of the nature of the ν=5/2 plateau. 
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