Friday, 20 September
11:00 AM - 2:00 PM
Room-5209
11:00 AM - 12:00 PM
Hydrodynamics of supersolids
Alan T. Dorsey, University of Georgia
In this talk, I will provide an overview of the search for supersolids, an elusive state of matter in which superfluid and solid behaviors coexist. Theoretical speculations on the coexistence of off-diagonal long-range order and crystalline order (with the accompanying shear rigidity) date from the 1960s; after a long dormant period, there was great excitement in 2004 when several experimental groups announced the observation of nonclassical rotational inertia, a hallmark of the putative supersolid phase, in samples of solid 4He. Alas, careful experiments from 2004-2012 determined that the signals of a supersolid phase were likely a result of defects in the solid that affected the shear modulus, with little to do with ODRLO. However, the experiments stimulated interest in a hydrodynamic theory of supersolids, with the identification of new collective modes. I will review this hydrodynamic theory, in which point defects in the solid play a starring role. I will also review recent work (Yoo and Dorsey, 2024) on vortex dynamics in two-dimensional supersolids. While not immediately relevant to solid 4He, variants of this work may be relevant to supersolid phases observed in dipolar atomic gases over the past five years.
12:00PM - 12:45 PM
Lunch
12:45 PM - 2:00 PM
Realizing topological physics in cavity QED
Michael Kolodrubetz
Topological properties of physical systems occur in a wide variety of settings, with robust measurable characteristics that depend on dimensionality, symmetries, and non-equilibrium drive. In this talk, I discuss two recent projects where we have studied the role of topology in cavity QED. In the first project, I introduce a topological phase known as the anomalous Floquet photon pump (AFPP) whose natural topological response involves quantized conversion of photons from one frequency to another. I discuss its connection to a more famous topological phase – the anomalous Floquet insulator – and introduce a very simple model for realizing the AFPP using a time-dependent Jaynes-Cummings Hamiltonian. In the second project, I consider the prospect of using topological edge modes in photonic cavity arrays to mediate long-range coupling between qubits. I show that an infinite-range RKKY-type interaction is mediated by topological edge modes in a photon Chern insulator and with magnitude that is unaffected by the distance between qubits. Away from perturbatively weak coupling of the qubits to the photons, I show that robust interactions persist with non-vanishing fidelity, suggesting a potential route to use topological edge modes for increasingly robust qubit-qubit interactions.
Please RSVP for the lunch.