10,029 research outputs found
Quantum Transport of Bosonic Cold Atoms in Double Well Optical Lattices
We numerically investigate, using the time evolving block decimation
algorithm, the quantum transport of ultra-cold bosonic atoms in a double well
optical lattice through slow and periodic modulation of the lattice parameters
(intra- and inter-well tunneling, chemical potential, etc.). The transport of
atoms does not depend on the rate of change of the parameters (as along as the
change is slow) and can distribute atoms in optical lattices at the quantized
level without involving external forces. The transport of atoms depends on the
atom filling in each double well and the interaction between atoms. In the
strongly interacting region, the bosonic atoms share the same transport
properties as non-interacting fermions with quantized transport at the half
filling and no atom transport at the integer filling. In the weakly interacting
region, the number of the transported atoms is proportional to the atom
filling. We show the signature of the quantum transport from the momentum
distribution of atoms that can measured in the time of flight image. A
semiclassical transport model is developed to explain the numerically observed
transport of bosonic atoms in the non-interacting and strongly interacting
limits. The scheme may serve as an quantized battery for atomtronics
applications.Comment: 8 pages, 9 figures, accepted for publication in Phys. Rev.
Berry Phase Effects on Electronic Properties
Ever since its discovery, the Berry phase has permeated through all branches
of physics. Over the last three decades, it was gradually realized that the
Berry phase of the electronic wave function can have a profound effect on
material properties and is responsible for a spectrum of phenomena, such as
ferroelectricity, orbital magnetism, various (quantum/anomalous/spin) Hall
effects, and quantum charge pumping. This progress is summarized in a
pedagogical manner in this review. We start with a brief summary of necessary
background, followed by a detailed discussion of the Berry phase effect in a
variety of solid state applications. A common thread of the review is the
semiclassical formulation of electron dynamics, which is a versatile tool in
the study of electron dynamics in the presence of electromagnetic fields and
more general perturbations. Finally, we demonstrate a re-quantization method
that converts a semiclassical theory to an effective quantum theory. It is
clear that the Berry phase should be added as a basic ingredient to our
understanding of basic material properties.Comment: 48 pages, 16 figures, submitted to RM
Calculation of the Branching Ratio of in PQCD
The branching ratio of is re-evaluated in the PQCD approach.
In this theoretical framework all the phenomenological parameters in the
wavefunctions and Sudakov factor are priori fixed by fitting other experimental
data, and in the whole numerical computations we do not introduce any new
parameter. Our results are consistent with the upper bounds set by the Babar
and Belle measurements.Comment: 12 pages, 1 figure, version to appear in Phys. Rev.
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