3,718 research outputs found
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
A mean field approach for string condensed states
We describe a mean field technique for quantum string (or dimer) models.
Unlike traditional mean field approaches, the method is general enough to
include string condensed phases in addition to the usual symmetry breaking
phases. Thus, it can be used to study phases and phases transitions beyond
Landau's symmetry breaking paradigm. We demonstrate the technique with a simple
example: the spin-1 XXZ model on the Kagome lattice. The mean field calculation
predicts a number of phases and phase transitions, including a z=2 deconfined
quantum critical point.Comment: 10 pages + appendix, 15 figure
Gauged Q ball in a piecewise parabolic potential
Q ball solutions are considered within the theory of a complex scalar field
with a gauged
U(1) symmetry and a parabolic-type potential. In the thin-walled limit, we
show explicitly that there is a maximum size for these objects because of the
repulsive Coulomb force. The size of Q ball will increase with the decrease of
local minimum of the potential. And when the two minima degenerate, the energy
stored within the surface of the Q ball becomes significant.
Furthermore, we find an analytic expression for gauged Q ball, which is
beyond the conventional thin-walled limit.Comment: 1 figure
Anyon Condensation and Continuous Topological Phase Transitions in Non-Abelian Fractional Quantum Hall States
We find a series of possible continuous quantum phase transitions between
fractional quantum Hall (FQH) states at the same filling fraction in
two-component quantum Hall systems. These can be driven by tuning the
interlayer tunneling and/or interlayer repulsion. One side of the transition is
the Halperin (p,p,p-3) Abelian two-component state while the other side is the
non-Abelian Z4 parafermion (Read-Rezayi) state. We predict that the transition
is a continuous transition in the 3D Ising class. The critical point is
described by a Z2 gauged Ginzburg-Landau theory. These results have
implications for experiments on two-component systems at \nu = 2/3 and
single-component systems at \nu = 8/3.Comment: 4 pages + ref
Transition Form Factor with Tensor Current within the Factorization Approach
In the paper, we apply the factorization approach to deal with the
transition form factor with tensor current in the large recoil
regions. Main uncertainties for the estimation are discussed and we obtain
, where the first error is caused by the
uncertainties from the pionic wave functions and the second is from that of the
B-meson wave functions. This result is consistent with the light-cone sum rule
results obtained in the literature.Comment: 8 pages, 4 figures, references adde
Quantum ether: photons and electrons from a rotor model
We give an example of a purely bosonic model -- a rotor model on the 3D cubic
lattice -- whose low energy excitations behave like massless U(1) gauge bosons
and massless Dirac fermions. This model can be viewed as a ``quantum ether'': a
medium that gives rise to both photons and electrons. It illustrates a general
mechanism for the emergence of gauge bosons and fermions known as ``string-net
condensation.'' Other, more complex, string-net condensed models can have
excitations that behave like gluons, quarks and other particles in the standard
model. This suggests that photons, electrons and other elementary particles may
have a unified origin: string-net condensation in our vacuum.Comment: 10 pages, 6 figures, RevTeX4. Home page http://dao.mit.edu/~we
Spontaneous spin ordering of Dirac spin liquid in a magnetic field
The Dirac spin liquid was proposed to be the ground state of the spin-1/2
Kagome antiferromagnets. In a magnetic field , we show that the state with
Fermi pocket is unstable to the Landau level (LL) state. The LL state breaks
the spin rotation around the axis of the magnetic field. We find that the LL
state has an in-plane 120 magnetization which scales with
the external field , where is an intrinsic
calculable universal number of the Dirac spin liquid. We discuss the related
experimental implications which can be used to detect the possible Dirac spin
liquid phase in Herbertsmithite ZnCu(OH)Cl.Comment: rewritten for clarit
- …