61,863 research outputs found
Structure of polydisperse inverse ferrofluids: Theory and computer simulation
By using theoretical analysis and molecular dynamics simulations, we
investigate the structure of colloidal crystals formed by nonmagnetic
microparticles (or magnetic holes) suspended in ferrofluids (called inverse
ferrofluids), by taking into account the effect of polydispersity in size of
the nonmagnetic microparticles. Such polydispersity often exists in real
situations. We obtain an analytical expression for the interaction energy of
monodisperse, bidisperse, and polydisperse inverse ferrofluids. Body-centered
tetragonal (bct) lattices are shown to possess the lowest energy when compared
with other sorts of lattices and thus serve as the ground state of the systems.
Also, the effect of microparticle size distributions (namely, polydispersity in
size) plays an important role in the formation of various kinds of structural
configurations. Thus, it seems possible to fabricate colloidal crystals by
choosing appropriate polydispersity in size.Comment: 22 pages, 8 figure
Magnetophoresis of nonmagnetic particles in ferrofluids
Ferrofluids containing nonmagnetic particles are called inverse ferrofluids.
On the basis of the Ewald-Kornfeld formulation and the Maxwell-Garnett theory,
we theoretically investigate the magnetophoretic force exerting on the
nonmagnetic particles in inverse ferrofluids due to the presence of a
nonuniform magnetic field, by taking into account the structural transition and
long-range interaction. We numerically demonstrate that the force can be
adjusted by choosing appropriate lattices, volume fractions, geometric shapes,
and conductivities of the nonmagnetic particles, as well as frequencies of
external magnetic fields.Comment: 24 pages, 7 figure
Coherent output of photons from coupled superconducting transmission line resonators controlled by charge qubits
We study the coherent control of microwave photons propagating in a
superconducting waveguide consisting of coupled transmission line resonators,
each of which is connected to a tunable charge qubit. While these coupled line
resonators form an artificial photonic crystal with an engineered photonic band
structure, the charge qubits collectively behave as spin waves in the low
excitation limit, which modify the band-gap structure to slow and stop the
microwave propagation. The conceptual exploration here suggests an
electromagnetically controlled quantum device based on the on-chip circuit QED
for the coherent manipulation of photons, such as the dynamic creation of
laser-like output from the waveguide by pumping the artificial atoms for
population inversion.Comment: 8 pages, 3 figure
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