Group Seminar Double Feature at LMU and Zoom: 1) Realization of 1D anyons with arbitrary statistical & 2) Frustration and kinetic magnetism in a Fermi-Hubbard Simulatorphase

August 29, 2023

Joyce Kwan and Martin Lebrat (Harvard University)
Group seminar at LMU seminar room and Zoom
Tuesday, August 29, 09:00 am (MEZ)


Joyce Kwan
Realization of 1D anyons with arbitrary statistical phase
Low-dimensional quantum systems can host anyons, particles with exchange statistics that are neither bosonic nor fermionic. Despite indications of a wealth of exotic phenomena, the physics of anyons in one dimension (1D) remains largely unexplored. In this talk, we present the first experimental realization of Abelian anyons in 1D using ultracold atoms in an optical lattice, where we engineer the statistical parameter via a density-dependent Peierls phase. Our scheme, based on Floquet engineering, allows for arbitrary exchange statistics and tunable interactions, which we leverage to explore the dynamical behavior of two anyons undergoing quantum walks. We observe the anyonic Hanbury Brown-Twiss effect and the formation of bound states without effective on-site interactions. Then, once interactions are introduced, we observe spatially asymmetric transport in contrast to the symmetric dynamics of bosons and fermions. Finally, we present ongoing work exploring ground state properties of these 1D anyons. Our work expands the toolset for Hamiltonian engineering, and enables the experimental exploration of the physics of 1D anyons.


Martin Lebrat
Frustration and kinetic magnetism in a Fermi-Hubbard Simulator
Geometrical frustration in strongly correlated systems can give rise to intriguing ordered states such as quantum spin liquids. In this talk, we report on recent experimental progress in Fermi gas microscopy demonstrating emergent magnetic states in a Hubbard model with controllable frustration and doping. Using an optical lattice continuously tunable from a square to a triangular geometry, we observe how geometrical frustration transforms a Néel antiferromagnet at half-filling into a short-range 120◦ spiral state. Away from half-filling, antiferromagnetic correlations in the triangular lattice are strengthened by hole dopants but surprisingly reverse to ferromagnetic when adding particle dopants. Through measurements of three-point dopant-spin-spin correlations, we reveal how these particle dopants are embedded into extended ferromagnetic bubbles resulting from the local interplay between coherent dopant motion and spin exchange. Such ferromagnetic polarons represent the first cold-atom observation of Nagaoka ferromagnetism, a paradigmatic model of itinerant magnetism with strong Hubbard interactions. Our work provides a microscopic picture of kinetic magnetism that has recently been observed in twisted TMD bilayers, and opens the way to investigating dopant pairing mediated by frustration.

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