1,533 research outputs found
Selective Population of Edge States in a 2D Topological Band System
We consider a system of interacting spin-one atoms in a hexagonal lattice
under the presence of a synthetic gauge field. Quenching the quadratic Zeeman
field is shown to lead to a dynamical instability of the edge modes. This, in
turn, leads to a spin current along the boundary of the system which grows
exponentially fast in time following the quench. Tuning the magnitude of the
quench can be used to selectively populate edge modes of different momenta.
Implications of the intrinsic symmetries of Hamiltonian on the dynamics are
discussed. The results hold for atoms with both antiferromagnetic and
ferromagnetic interactions.Comment: 7 pages (expanded Supplemental Material
Transport phenomenology for a holon-spinon fluid
We propose that the normal-state transport in the cuprate superconductors can
be understood in terms of a two-fluid model of spinons and holons. In our
scenario, the resistivity is determined by the properties of the holons while
magnetotransport involves the recombination of holons and spinons to form
physical electrons. Our model implies that the Hall transport time is a measure
of the electron lifetime, which is shorter than the longitudinal transport
time. This agrees with our analysis of the normal-state data. We predict a
strong increase in linewidth with increasing temperature in photoemission. Our
model also suggests that the AC Hall effect is controlled by the transport
time.Comment: 4 pages, 1 postscript figure. Uses RevTeX, epsf, multico
Dissipation and Tunnelling in Quantum Hall Bilayers
We discuss the interplay between transport and intrinsic dissipation in
quantum Hall bilayers, within the framework of a simple thought experiment. We
compute, for the first time, quantum corrections to the semiclassical dynamics
of this system. This allows us to re-interpret tunnelling measurements on these
systems. We find a strong peak in the zero-temperature tunnelling current that
arises from the decay of Josephson-like oscillations into incoherent charge
fluctuations. In the presence of an in-plane field, resonances in the
tunnelling current develop an asymmetric lineshape.Comment: 4 pages, 3 figure
Quantised Bulk Conductivity as a Local Chern Marker
A central property of Chern insulators is the robustness of the topological
phase and edge states to impurities in the system. Despite this, Chern number
cannot be straightforwardly calculated in the presence of disorder. Recently,
work has been done to propose a local analog of the Chern number, called local
markers, that can be used to characterise disordered systems. However, it was
unclear whether the proposed markers represented a physically-measurable
property of the system. Here we propose a local marker starting from a physical
argument, as a local cross-conductivity measured in the bulk of the system. We
find the explicit form of the marker for a non-interacting system of electrons
on the lattice and show that it corresponds to existing expressions for the
Chern number. Examples are calculated for a variety of disordered and amorphous
systems, showing that it is precisely quantised to the Chern number and robust
against disorder.Comment: 10 pages, 9 figure
Quantum and Classical Dissipative Effects on Tunnelling in Quantum Hall Bilayers
We discuss the interplay between transport and dissipation in quantum Hall
bilayers. We show that quantum effects are relevant in the pseudospin picture
of these systems, leading either to direct tunnelling currents or to quantum
dissipative processes that damp oscillations around the ground state. These
quantum effects have their origins in resonances of the classical spin system.Comment: 12 pages. Minor changes from v
On a Network Model of Localization in a Random Magnetic Field
We consider a network model of snake states to study the localization problem
of non-interacting fermions in a random magnetic field with zero average. After
averaging over the randomness, the network of snake states is mapped onto
coupled SU spin chains in the limit. The number of
snake states near the zero-field contour, , is an even integer. In the large
conductance limit (), it turns out
that this system is equivalent to a particular representation of the sigma model () {\it
without} a topological term. The beta function of this sigma
model in the expansion is consistent with the previously known of the unitary ensemble. These results and further plausible arguments
support the conclusion that all the states are localized.Comment: Revtex, 6 pages, 3 figures appended as an uuencoded fil
Hyperbolic calorons, monopoles, and instantons
We construct families of SO(3)-symmetric charge 1 instantons and calorons on
the space H^3 x R. We show how the calorons include instantons and hyperbolic
monopoles as limiting cases. We show how Euclidean calorons are the flat space
limit of this family.Comment: 11 pages, no figures 1 reference added Published version available
at: http://www.springerlink.com/content/k0j4815u54303450
Active Response Gravity Offload and Method
A variable gravity field simulator can be utilized to provide three dimensional simulations for simulated gravity fields selectively ranging from Moon, Mars, and micro-gravity environments and/or other selectable gravity fields. The gravity field simulator utilizes a horizontally moveable carriage with a cable extending from a hoist. The cable can be attached to a load which experiences the effects of the simulated gravity environment. The load can be a human being or robot that makes movements that induce swinging of the cable whereby a horizontal control system reduces swinging energy. A vertical control system uses a non-linear feedback filter to remove noise from a load sensor that is in the same frequency range as signals from the load sensor
Degenerate Bose liquid in a fluctuating gauge field
We study the effect of a strongly fluctuating gauge field on a degenerate
Bose liquid, relevant to the charge degrees of freedom in doped Mott
insulators. We find that the superfluidity is destroyed. The resulting metallic
phase is studied using quantum Monte Carlo methods. Gauge fluctuations cause
the boson world lines to retrace themselves. We examine how this world-line
geometry affects the physical properties of the system. In particular, we find
a transport relaxation rate of the order of 2kT, consistent with the normal
state of the cuprate superconductors. We also find that the density excitations
of this model resemble that of the full tJ model.Comment: 4 pages. Uses RevTeX, epsf, multicols macros. 5 postscript figure
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