18,914 research outputs found
Directional `superradiant' collisions: bosonic amplification of atom pairs emitted from an elongated Bose-Einstein condensate
We study spontaneous directionality in the bosonic amplification of atom
pairs emitted from an elongated Bose-Einstein condensate (BEC), an effect
analogous to `superradiant' emission of atom-photon pairs. Using a simplified
model, we make analytic predictions regarding directional effects for both
atom-atom and atom-photon emission. These are confirmed by numerical mean-field
simulations, demonstrating the the feasibility of nearly perfect directional
emission along the condensate axis. The dependence of the emission angle on the
pump strength for atom-atom pairs is significantly different than for
atom-photon pairs
Projective non-Abelian Statistics of Dislocation Defects in a Z_N Rotor Model
Non-Abelian statistics is a phenomenon of topologically protected non-Abelian
Berry phases as we exchange quasiparticle excitations. In this paper, we
construct a Z_N rotor model that realizes a self-dual Z_N Abelian gauge theory.
We find that lattice dislocation defects in the model produce topologically
protected degeneracy. Even though dislocations are not quasiparticle
excitations, they resemble non-Abelian anyons with quantum dimension sqrt(N).
Exchanging dislocations can produces topologically protected projective
non-Abelian Berry phases. The dislocations, as projective non-Abelian anyons
can be viewed as a generalization of the Majorana zero modes.Comment: 4 pages + refs, 4 figures. RevTeX
Effective Hamiltonian Approach to the Master Equation
A method of exactly solving the master equation is presented in this letter.
The explicit form of the solution is determined by the time evolution of a
composite system including an auxiliary system and the open system in question.
The effective Hamiltonian governing the time evolution of the composed system
are derived from the master equation. Two examples, the dissipative two-level
system and the damped harmonic oscillator, are presented to illustrate the
solving procedure.
PACS number(s): 05.30.-d, 05.40.+j, 42.50.CtComment: 4 pages, no figure
Doping a spin-orbit Mott Insulator: Topological Superconductivity from the Kitaev-Heisenberg Model and possible application to (Na2/Li2)IrO3
We study the effects of doping a Mott insulator on the honeycomb lattice
where spins interact via direction dependent Kitaev couplings J_K, and weak
antiferromagnetic Heisenberg couplings J. This model is known to have a spin
liquid ground state and may potentially be realized in correlated insulators
with strong spin orbit coupling. The effect of hole doping is studied within a
t-J-J_K model, treated using the SU(2) slave boson formulation, which correctly
captures the parent spin liquid. We find superconductor ground states with spin
triplet pairing that spontaneously break time reversal symmetry. Interestingly,
the pairing is qualitatively different at low and high dopings, and undergoes a
first order transition with doping. At high dopings, it is smoothly connected
to a paired state of electrons propagating with the underlying free particle
dispersion. However, at low dopings the dispersion is strongly influenced by
the magnetic exchange, and is entirely different from the free particle band
structure. Here the superconductivity is fully gapped and topological,
analogous to spin polarized electrons with px+ipy pairing. These results may be
relevant to honeycomb lattice iridates such as A2IrO3 (A=Li or Na) on doping.Comment: 8 pages + 6 pages supplementary material; 5 figures, 3 tabl
The direct algorithm to construct the Davey-Stewartson hierarchy by two scalar pseudo-differential operators
The infinite many symmetries of DS(Davey-Stewartson) system are closely
connected to the integrable deformations of surfaces in . In
this paper, we give a direct algorithm to construct the expression of the
DS(Davey-Stewartson) hierarchy by two scalar pseudo-differential operators
involved with and .Comment: 16 page
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