6,042 research outputs found
Precision measurement of charge number with optomechanically induced transparency
We propose a potentially practical scheme to precisely measure the charge
numbers of small charged objects by optomechanical systems using
optomechanically induced transparency (OMIT). In contrast to the conventional
measurements based on the noise backaction on the optomechanical systems, our
scheme makes use of the small deformation of the mechanical resonator sensitive
to the charge number of the nearby charged object, which could achieve the
detection of a single charge. The relationship between the charge number and
the window width of the OMIT is investigated and the feasibility of the scheme
is justified by numerical simulation using currently available experimental
values.Comment: 6 pages,4 figure
Intriguing Heat Conduction of a Polymer Chain
We study heat conduction in a one-dimensional chain of particles with
longitudinal as well as transverse motions. The particles are connected by
two-dimensional harmonic springs together with bending angle interactions.
Using equilibrium and nonequilibrium molecular dynamics, three types of thermal
conducting behaviors are found: a logarithmic divergence with system sizes for
large transverse coupling, 1/3 power-law at intermediate coupling, and 2/5
power-law at low temperatures and weak coupling. The results are consistent
with a simple mode-coupling analysis of the same model. The 1/3 power-law
divergence should be a generic feature for models with transverse motions.Comment: 4 page
Counting Rule for Hadronic Light-Cone Wave Functions
We introduce a systematic way to write down the Fock components of a hadronic
light-cone wave function with partons and orbital angular momentum
projection . We show that the wave function amplitude
has a leading behavior
when all parton transverse
momenta are uniformly large, where and are the number of partons
and orbital angular momentum projection, respectively, of an amplitude that
mixes under renormalization. The result can be used as a constraint in modeling
the hadronic light-cone wave functions. We also derive a generalized counting
rule for hard exclusive processes involving parton orbital angular momentum and
hadron helicity flip.Comment: 7 pages, no figur
Pairing Symmetry in Iron-Pnictide Superconductor KFeAs
The pairing symmetry is one of the major issues in the study of iron-based
superconductors. We adopt a low-energy effective kinetic model based on the
first-principles band structure calculations combined with the -
model for KFeAs, the phase diagram of pairing symmetries is
constructed. Putting the values of and of the - model
obtained by the first-principles calculations into this phase diagram, we find
that the pairing symmetry for KFeAs is a nodal -wave in the
folded Brillouin zone with two iron atoms per unit cell. This is in good
agreement with experiments observed a nodal order parameter.Comment: 5 pages, 4 figures (The pairing symmetry is dependent on choosing an
effective tight-binding model. In the publication version, we adopt a
ten-orbital model by using the maximally localized Wannier functions based on
the first-principles band structure calculations, and give an s-wave pairing
for KFeAs
Simultaneous readout of two charge qubits
We consider a system of two solid state charge qubits, coupled to a single
read-out device, consisting of a single-electron transistor (SET). The
conductance of each tunnel junction is influenced by its neighboring qubit, and
thus the current through the transistor is determined by the qubits' state. The
full counting statistics of the electrons passing the transistor is calculated,
and we discuss qubit dephasing, as well as the quantum efficiency of the
readout. The current measurement is then compared to readout using real-time
detection of the SET island's charge state. For the latter method we show that
the quantum efficiency is always unity. Comparing the two methods a simple
geometrical interpretation of the quantum efficiency of the current measurement
appears. Finally, we note that full quantum efficiency in some cases can be
achieved measuring the average charge of the SET island, in addition to the
average current.Comment: 11 pages with 5 figure
New application of decomposition of U(1) gauge potential:Aharonov-Bohm effect and Anderson-Higgs mechanism
In this paper we study the Aharonov-Bohm (A-B) effect and Anderson-Higgs
mechanism in Ginzburg-Landau model of superconductors from the perspective of
the decomposition of U(1) gauge potential. By the Helmholtz theorem, we derive
exactly the expression of the transverse gauge potential in A-B
experiment, which is gauge-invariant and physical. For the case of a bulk
superconductor, we find that the gradient of the total phase field
provides the longitudinal component , which reflects the
Anderson-Higgs mechanism. For the case of a superconductor ring, the gradient
of the longitudinal phase field provides the longitudinal component
, while the transverse phase field produces
new physical effects such as the flux quantization inside a superconducting
ring.Comment: 6 pages, no figures, final version to appear in Modern Physics
Letters
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