School of Natural Sciences and Mathematics

Permanent URI for this communityhttps://hdl.handle.net/10735.1/1347

Treasures metadata is created using UTF-8 (Unicode) characters. It is suggested that for best viewing of items a font with a large amount of unicode characters (e.g. Arial Unicode MS, FreeSerif, or NotoSerif) be made the default font in your browser. When scientific formulas cannot be rendered in unicode, they will be coded in LaTeX.

Browse

Browsing School of Natural Sciences and Mathematics by Author "0000 0000 3722 2361 (Zhang, C)"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Momentum-Space Josephson Effects
    (Amer Physical Soc) Hou, Junpeng; Luo, Xi-Wang; Sun, Kuei; Bersano, Thomas; Gokhroo, Vandna; Mossman, Sean; Engels, Peter; Zhang, Chuanwei; 0000 0000 3722 2361 (Zhang, C); 4042455 (Zhang, C); Hou, Junpeng; Luo, Xi-Wang; Sun, Kuei; Zhang, Chuanwei
    The Josephson effect is a prominent phenomenon of quantum supercurrents that has been widely studied in superconductors and superfluids. Typical Josephson junctions consist of two real-space superconductors (superfluids) coupled through a weak tunneling barrier. Here we propose a momentum-space Josephson junction in a spin-orbit coupled Bose-Einstein condensate, where states with two different momenta are coupled through Raman-assisted tunneling. We show that Josephson currents can be induced not only by applying the equivalent of "voltages," but also by tuning tunneling phases. Such tunneling-phase-driven Josephson junctions in momentum space are characterized through both full mean field analysis and a concise two-level model, demonstrating the important role of interactions between atoms. Our scheme provides a platform for experimentally realizing momentum-space Josephson junctions and exploring their applications in quantum-mechanical circuits.
  • Thumbnail Image
    Item
    Spin-Orbit-Driven Transitions between Mott Insulators and Finite-Momentum Superfluids of Bosons in Optical Lattices
    (Amer Physical Soc, 2018-11-05) Yan, Mi; Qian, Yinyin; Hui, Hoi-Yin; Gong, Ming; Zhang, Chuanwei; Scarola, V. W.; 0000 0000 3722 2361 (Zhang, C); 4042455 (Zhang, C); Qian, Yinyin; Gong, Ming; Zhang, Chuanwei
    Synthetic spin-orbit coupling in ultracold atomic gases can be taken to extremes rarely found in solids. We study a two-dimensional Hubbard model of bosons in an optical lattice in the presence of spin-orbit coupling strong enough to drive direct transitions from Mott insulators to superfluids. Here we find phase-modulated superfluids with finite momentum that are generated entirely by spin-orbit coupling. We investigate the rich phase patterns of the superfluids, which may be directly probed using time-of-flight imaging of the spin-dependent momentum distribution.
  • Thumbnail Image
    Item
    Superfluidity in the Absence of Kinetics in Spin-Orbit-Coupled Optical Lattices
    (Amer Physical Soc) Hui, Hoi-Yin; Zhang, Yongping; Zhang, Chuanwei; Scarola, V. W.; 0000 0000 3722 2361 (Zhang, C); 4042455 (Zhang, C); Zhang, Chuanwei
    At low temperatures bosons typically condense to minimize their single-particle kinetic energy while interactions stabilize superfluidity. Optical lattices with artificial spin-orbit coupling challenge this paradigm, because here kinetic energy can be quenched in an extreme regime where the single-particle band flattens. To probe the fate of superfluidity in the absence of kinetics we construct and numerically solve interaction-only tight-binding models in flatbands. We find that superfluid states arise entirely from interactions operating in quenched kinetic energy bands, thus revealing a distinct and unexpected condensation mechanism. Our results have important implications for the identification of quantum condensed phases of ultracold bosons beyond conventional paradigms.
  • Thumbnail Image
    Item
    Topological Triply Degenerate Points Induced by Spin-Tensor- Momentum Couplings
    (Amer Physical Soc) Hu, Haiping; Hou, Junpeng; Zhang, Fan; Zhang, Chuanwei; 0000 0000 3722 2361 (Zhang, C); 0000-0003-4623-4200 (Zhang, F); 4042455 (Zhang, C); Hu, Haiping; Hou, Junpeng; Zhang, Fan; Zhang, Chuanwei
    The recent discovery of triply degenerate points (TDPs) in topological materials has opened a new perspective toward the realization of novel quasiparticles without counterparts in quantum field theory. The emergence of such protected nodes is often attributed to spin-vector-momentum couplings. We show that the interplay between spin-tensor-and spin-vector-momentum couplings can induce three types of TDPs, classified by different monopole charges (C = ± 2, ± 1, 0). A Zeeman field can lift them into Weyl points with distinct numbers and charges. Different TDPs of the same type are connected by intriguing Fermi arcs at surfaces, and transitions between different types are accompanied by level crossings along high-symmetry lines. We further propose an experimental scheme to realize such TDPs in cold-atom optical lattices. Our results provide a framework for studying spin-tensor-momentum coupling-induced TDPs and other exotic quasiparticles.