32,412 research outputs found
Dissipation Effects in Hybrid Systems
The dissipation effect in a hybrid system is studied in this Letter. The
hybrid system is a compound of a classical magnetic particle and a quantum
single spin. Two cases are considered. In the first case, we investigate the
effect of the dissipative quantum subsystem on the motion of its classical
partner. Whereas in the second case we show how the dynamics of the quantum
single spin are affected by the dissipation of the classical particle.
Extension to general dissipative hybrid systems is discussed.Comment: 4+ pages, 4 figure
BCS-BEC crossover and quantum phase transition for 6Li and 40K atoms across Feshbach resonance
We systematically study the BCS-BEC crossover and the quantum phase
transition in ultracold 6Li and 40K atoms across a wide Feshbach resonance. The
background scattering lengths for 6Li and 40K have opposite signs, which lead
to very different behaviors for these two types of atoms. For 40K, both the
two-body and the many-body calculations show that the system always has two
branches of solutions: one corresponds to a deeply bound molecule state; and
the other, the one accessed by the current experiments, corresponds to a weakly
bound state with population always dominantly in the open channel. For 6Li,
there is only a unique solution with the standard crossover from the weakly
bound Cooper pairs to the deeply bound molecules as one sweeps the magnetic
field through the crossover region. Because of this difference, for the
experimentally accessible state of 40K, there is a quantum phase transition at
zero temperature from the superfluid to the normal fermi gas at the positive
detuning of the magnetic field where the s-wave scattering length passes its
zero point. For 6Li, however, the system changes continuously across the zero
point of the scattering length. For both types of atoms, we also give detailed
comparison between the results from the two-channel and the single-channel
model over the whole region of the magnetic field detuning.Comment: 7 pages, 6 figure
Geometric phases induced in auxiliary qubits by many-body systems near its critical points
The geometric phase induced in an auxiliary qubit by a many-body system is
calculated and discussed. Two kinds of coupling between the auxiliary qubit and
the many-body system are considered, which lead to dephasing and dissipation in
the qubit, respectively. As an example, we consider the XY spin-chain
dephasingly couple to a qubit, the geometric phase induced in the qubit is
presented and discussed. The results show that the geometric phase might be
used to signal the critical points of the many-body system, and it tends to
zero with the parameters of the many-body system going away from the critical
points
Phase diagram of a polarized Fermi gas across a Feshbach resonance in a potential trap
We map out the detailed phase diagram of a trapped ultracold Fermi gas with
population imbalance across a wide Feshbach resonance. We show that under the
local density approximation, the properties of the atoms in any (anisotropic)
harmonic traps are universally characterized by three dimensionless parameters:
the normalized temperature, the dimensionless interaction strength, and the
population imbalance. We then discuss the possible quantum phases in the trap,
and quantitatively characterize their phase boundaries in various typical
parameter regions.Comment: 9 pages, 4 figure
Dissipation-induced d-Wave Pairing of Fermionic Atoms in an Optical Lattice
We show how dissipative dynamics can give rise to pairing for two-component
fermions on a lattice. In particular, we construct a "parent" Liouvillian
operator so that a BCS-type state of a given symmetry, e.g. a d-wave state, is
reached for arbitrary initial states in the absence of conservative forces. The
system-bath couplings describe single-particle, number conserving and
quasi-local processes. The pairing mechanism crucially relies on Fermi
statistics. We show how such Liouvillians can be realized via reservoir
engineering with cold atoms representing a driven dissipative dynamics.Comment: 5 pages, 3 figures. Replaced with the published versio
Vanishing Hawking Radiation from a Uniformly Accelerated Black Hole
We consider quantum fields around uniformly accelerated black holes. At a
particular value of the acceleration, the Bogolubov transformation which would
be responsible for the late-time Hawking radiation, is found to be trivial.
When this happens, Hawking's thermal radiation, Doppler-shifted or not, is
absent to the asymptotic inertial observers despite the nonzero Hawking
temperature, while the co-moving observers find the black hole radiance exactly
balanced by the acceleration heat bath. After a brief comparison to the
classical system of a uniformly accelerated charge, we close with two important
comments. (Phys. Rev. Lett. 75 (1995) 382)Comment: LaTeX, 10pages, 2 figures (a typo in Eq.(3) corrected; minor
revisions to accomodate the length limitation of the journal
Impact of intrinsic biophysical diversity on the activity of spiking neurons
We study the effect of intrinsic heterogeneity on the activity of a
population of leaky integrate-and-fire neurons. By rescaling the dynamical
equation, we derive mathematical relations between multiple neuronal parameters
and a fluctuating input noise. To this end, common input to heterogeneous
neurons is conceived as an identical noise with neuron-specific mean and
variance. As a consequence, the neuronal output rates can differ considerably,
and their relative spike timing becomes desynchronized. This theory can
quantitatively explain some recent experimental findings.Comment: 4 pages, 5 figure
Suppression of ferromagnetic ordering in doped manganites: Effects of the superexchange interaction
From a Monte Carlo study of the ferromagnetic Kondo lattice model for doped
manganites, including the antiferromagnetic superexchange interaction
(), we found that the ferromagnetic ordering was suppressed as
increased. The ferromagnetic transition temperature , as obtained from a
mean field fit to the calculated susceptibilities, was found to decrease
monotonically with increasing . Further, the suppression in
scales with the bandwidth narrowing induced by the antiferromagnetic
frustration originating from . From these results, we propose that the
change in the superexchange interaction strength between the electrons
of the Mn ions is one of the mechanisms responsible for the suppression in
observed in manganites of the type
(LaPr)CaMnO.Comment: 5 pages, 6 figures. To appear in PR
- …