844 research outputs found
Topological superfluid in a fermionic bilayer optical lattice
In this paper, a topological superfluid phase with Chern number C=1
possessing gapless edge states and non-Abelian anyons is designed in a C=1
topological insulator proximity to an s-wave superfluid on an optical lattice
with the effective gauge field and layer-dependent Zeeman field coupled to
ultracold fermionic atoms pseudo spin. We also study its topological properties
and calculate the phase stiffness by using the random-phase-approximation
approach. Finally we derive the temperature of the Kosterlitz-Thouless
transition by means of renormalized group theory. Owning to the existence of
non-Abelian anyons, this C=1 topological superfluid may be a possible candidate
for topological quantum computation.Comment: 15 pages, 8 figure
Structural constraints on the emergence of oscillations in multi-population neural networks
Oscillations arise in many real-world systems and are associated with both
functional and dysfunctional states. Whether a network can oscillate can be
estimated if we know the strength of interaction between nodes. But in
real-world networks (in particular in biological networks) it is usually not
possible to know the exact connection weights. Therefore, it is important to
determine the structural properties of a network necessary to generate
oscillations. Here, we provide a proof that uses dynamical system theory to
prove that an odd number of inhibitory nodes and strong enough connections are
necessary to generate oscillations in a single cycle threshold-linear network.
We illustrate these analytical results in a biologically plausible network with
either firing-rate based or spiking neurons. Our work provides structural
properties necessary to generate oscillations in a network. We use this
knowledge to reconcile recent experimental findings about oscillations in basal
ganglia with classical findings.Comment: Main text: 30 pages, 5 Figures. Supplementary information: 20 pages,
9 Figures. Supplementary Information is integrated in the main fil
Stretchable and High-Performance Supercapacitors with Crumpled Graphene Papers
Fabrication of unconventional energy storage devices with high stretchability and performance is challenging, but critical to practical operations of fully power-independent stretchable electronics. While supercapacitors represent a promising candidate for unconventional energy-storage devices, existing stretchable supercapacitors are limited by their low stretchability, complicated fabrication process, and high cost. Here, we report a simple and low-cost method to fabricate extremely stretchable and high-performance electrodes for supercapacitors based on new crumpled-graphene papers. Electrolyte-mediated-graphene paper bonded on a compliant substrate can be crumpled into self-organized patterns by harnessing mechanical instabilities in the graphene paper. As the substrate is stretched, the crumpled patterns unfold, maintaining high reliability of the graphene paper under multiple cycles of large deformation. Supercapacitor electrodes based on the crumpled graphene papers exhibit a unique combination of high stretchability (e.g., linear strain ~300%, areal strain ~800%), high electrochemical performance (e.g., specific capacitance ~196 F g[superscript −1]), and high reliability (e.g., over 1000 stretch/relax cycles). An all-solid-state supercapacitor capable of large deformation is further fabricated to demonstrate practical applications of the crumpled-graphene-paper electrodes. Our method and design open a wide range of opportunities for manufacturing future energy-storage devices with desired deformability together with high performance.United States. Office of Naval Research (N00014-14-1-0619)National Science Foundation (U.S.) (CMMI-1253495)National Science Foundation (U.S.) (DMR-1121107)National Science Foundation (U.S.) (EECS-1344745
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