Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session J10: Flat Band Effects in Ultracold Atomic and Solid-State MaterialsInvited Live
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Sponsoring Units: DAMOP Chair: Dan Stamper-Kurn, University of California, Berkeley |
Tuesday, March 16, 2021 3:00PM - 3:36PM Live |
J10.00001: Quantum distance and anomalous Landau levels of flat bands Invited Speaker: Bohm-Jung Yang Semiclassical quantization of electronic states under a magnetic field describes not only the Landau level spectrum but also the geometric responses of metals under a magnetic field. Even in graphene with relativistic energy dispersion, Onsager’s rule correctly describes the π Berry phase, as well as the unusual Landau level spectrum of Dirac particles. However, it is unclear whether this semiclassical idea is valid in dispersionless flat-band systems, in which an infinite number of degenerate semiclassical orbits are allowed. Here we show that the semiclassical quantization rule breaks down for a class of dispersionless flat bands. The Landau levels of such a flat band develop in the empty region in which no electronic states exist in the absence of a magnetic field, and exhibit an unusual dependence on the Landau level index n, which results in anomalous orbital magnetic susceptibility. The total energy spread of the Landau levels of flat bands is determined by the geometry of the relevant Bloch states, which is characterized by their Hilbert–Schmidt quantum distance. The results indicate that the anomalous Landau level spectrum of flat bands is promising for the direct measurement of the geometry of wavefunctions in condensed matter. |
Tuesday, March 16, 2021 3:36PM - 4:12PM Live |
J10.00002: Ultracold atoms in Lieb lattices Invited Speaker: Shintaro Taie Ultracold atoms in optical lattices have been attracted much interest for its application to quantum simulation, in which non-trivial theoretical models are simulated by well-controllable quantum systems instead of getting hardly-computable numerical solutions. Optical lattices provide a unique opportunity to simulate strongly correlated solid electrons, especially those described by the Hubbard model. |
Tuesday, March 16, 2021 4:12PM - 4:48PM Live |
J10.00003: Interaction-Enhanced Group Velocity of Bosons in the Flat Band of an Optical Kagome Lattice Invited Speaker: Tsz-Him Leung Geometric frustration of particle motion in a kagome lattice causes the single-particle band structure to have a flat s-orbital band. We probe this band structure by placing a Bose-Einstein condensate into excited Bloch states of an optical kagome lattice, and then measuring the group velocity through the atomic momentum distribution. We find that interactions renormalize the band structure, greatly increasing the dispersion of the third band, which is nearly non-dispersing the single-particle treatment. Calculations based on the lattice Gross-Pitaevskii equation indicate that band structure renormalization is caused by the distortion of the overall lattice potential away from the kagome geometry by interactions. |
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