115 research outputs found
Reentrant topological transitions with Majorana end states in 1D superconductors by lattice modulation
The possibility to observe and manipulate Majorana fermions as end states of
one-dimensional topological superconductors has been actively discussed
recently. In a quantum wire with strong spin-orbit coupling placed in proximity
to a bulk superconductor, a topological superconductor has been expected to be
realized when the band energy is split by the application of a magnetic field.
When a periodic lattice modulation is applied multiple topological
superconductor phases appear in the phase diagram. Some of them occur for
higher filling factors compared to the case without the modulation. We study
the effects of phase jumps and argue that the topologically nontrivial state of
the whole system is retained even if they are present. We also study the effect
of the spatial modulation in the hopping parameter.Comment: 10 pages, 9 figures, submitted to Phys. Rev.
Reentrant topological transitions in a quantum wire/superconductor system with quasiperiodic lattice modulation
We study the condition for a topological superconductor (TS) phase with end
Majorana fermions to appear when a quasiperiodic lattice modulation is applied
to a one-dimensional quantum wire with strong spin-orbit interaction situated
under a magnetic field and in proximity to a superconductor. By density-matrix
renormalization group analysis, we find that multiple topological phases with
Majorana end modes are realized in finite ranges of the filling factor, showing
a sequence of reentrant transitions as the chemical potential is tuned. The
locations of these phases reflect the structure of bands in the non-interacting
case, which exhibits a distinct self-similar structure. The stability of the TS
in the presence of an on-site interaction or a harmonic trap potential is also
discussed.Comment: 5 pages, 4 figures, v4: minor corrections; published in Phys. Rev. B
Rapid Communicatio
Drag dynamics in one-dimensional Fermi systems
We study drag dynamics of several fermions in a fermion cloud in
one-dimensional continuous systems, with particular emphasis on the non-trivial
quantum many-body effects in systems whose parameters change gradually in real
time. We adopt the Fermi--Hubbard model and the time-dependent density matrix
renormalization group method to calculate the drag force on a trapped fermion
cluster in a cloud of another fermion species with contact interaction. The
simulation result shows that a non-trivial peak in the resistance force is
observed in the high cloud density region, which implies a criterion of
effective ways in diffusive transport in a fermion cloud. We compare the DMRG
simulation result with a mean-field result, and it is suggested that some
internal degrees of freedom have a crucial role in the excitation process when
the cloud density is high. This work emphasizes the difference between the
full-quantum calculation and the semiclassical calculation, which is the
quantum effects, in slow dynamics of many-body systems bound in a fermion
cloud.Comment: 7 pages, 8 figure
Density-Matrix Renormalization Group Study of Trapped Imbalanced Fermi Condensates
The density-matrix renormalization group is employed to investigate a
harmonically-trapped imbalanced Fermi condensate based on a one-dimensional
attractive Hubbard model. The obtained density profile shows a flattened
population difference of spin-up and spin-down components at the center of the
trap, and exhibits phase separation between the condensate and unpaired
majority atoms for a certain range of the interaction and population imabalance
. The two-particle density matrix reveals that the sign of the order
parameter changes periodically, demonstrating the realization of the
Fulde-Ferrell-Larkin-Ovchinnikov phase. The minority spin atoms contribute to
the quasi-condensate up to at least . Possible experimental
situations to test our predictions are discussed.Comment: 4 pages, 3 figures; added references; accepted for publication in
Phys. Rev. Let
Disposable collection kit for rapid and reliable collection of saliva.
ObjectivesTo describe and evaluate disposable saliva collection kit for rapid, reliable, and reproducible collection of saliva samples.MethodsThe saliva collection kit comprised of a saliva absorbent swab and an extractor unit was used to retrieve whole saliva samples from 10 subjects. The accuracy and precision of the extracted volumes (3, 10, and 30 μl) were compared to similar volumes drawn from control samples obtained by passive drool. Additionally, the impact of kit collection method on subsequent immunoassay results was verified by assessing salivary cortisol levels in the samples and comparing them to controls.ResultsThe recovered volumes for the whole saliva samples were 3.85 ± 0.28, 10.79 ± 0.95, and 31.18 ± 1.72 μl, respectively (CV = 8.76%) and 2.91 ± 0.19, 9.75 ± 0.43, and 29.64 ± 0.91 μl, respectively, (CV = 6.36%) for the controls. There was a close correspondence between the salivary cortisol levels from the saliva samples obtained by the collection kit and the controls (R(2) > 0.96).ConclusionsThe disposable saliva collection kit allows accurate and repeatable collection of fixed amounts of whole saliva and does not interfere with subsequent measurements of salivary cortisol. The simple collection process, lack of elaborate specimen recovery steps, and the short turnaround time (<3 min) should render the kit attractive to test subjects and researchers alike
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