26 research outputs found
Dynamical Casimir effect for magnons in a spinor Bose-Einstein condensate
Magnon excitation in a spinor Bose-Einstein condensate by a driven magnetic
field is shown to have a close analogy with the dynamical Casimir effect. A
time-dependent external magnetic field amplifies quantum fluctuations in the
magnetic ground state of the condensate, leading to magnetization of the
system. The magnetization occurs in a direction perpendicular to the magnetic
field breaking the rotation symmetry. This phenomenon is numerically
demonstrated and the excited quantum field is shown to be squeezed.Comment: 8 pages, 3 figure
Optical Aharonov-Bohm Effect on Wigner Molecules in Type-II Semiconductor Quantum Dots
We theoretically examine the magnetoluminescence from a trion and a biexciton
in a type-II semiconductor quantum dot, in which holes are confined inside the
quantum dot and electrons are in a ring-shaped region surrounding the quantum
dot. First, we show that two electrons in the trion and biexciton are strongly
correlated to each other, forming a Wigner molecule: Since the relative motion
of electrons is frozen, they behave as a composite particle whose mass and
charge are twice those of a single electron. As a result, the energy of the
trion and biexciton oscillates as a function of magnetic field with half the
period of the single-electron Aharonov-Bohm oscillation. Next, we evaluate the
photoluminescence. Both the peak position and peak height change
discontinuously at the transition of the many-body ground state, implying a
possible observation of the Wigner molecule by the optical experiment.Comment: 10 pages, 10 figures, accepted for publication in Phys. Rev.
Diffusion Enhances Chirality Selection
Diffusion effect on chirality selection in a two-dimensional
reaction-diffusion model is studied by the Monte Carlo simulation. The model
consists of achiral reactants A which turn into either of the chiral products,
R or S, in a solvent of chemically inactive vacancies V. The reaction contains
the nonlinear autocatalysis as well as recycling process, and the chiral
symmetry breaking is monitored by an enantiomeric excess .
Without dilution a strong nonlinear autocatalysis ensures chiral symmetry
breaking. By dilution, the chiral order decreases, and the racemic state
is recovered below the critical concentration . Diffusion effectively
enhances the concentration of chiral species, and decreases as the
diffusion coefficient increases. The relation between and for a
system with a finite fits rather well to an interpolation formula between
the diffusionless(D=0) and homogeneous () limits.Comment: 7 pages, 6 figure
Magnetoluminescence from trion and biexciton in type-II quantum dot
We theoretically investigate optical Aharonov-Bohm (AB) effects on trion and biexciton in the type-II semiconductor quantum dots, in which holes are localized near the center of the dot, and electrons are confined in a ring structure formed around the dot. Many-particle states are calculated numerically by the exact diagonalization method. Two electrons in trion and biexciton are strongly correlated to each other, forming a Wigner molecule. Since the relative motion of electrons are frozen, the Wigner molecule behaves as a composite particle whose mass and charges are twice those of an electron. As a result, the period of AB oscillation for trion and biexciton becomes h/2e as a function of magnetic flux penetrating the ring. We find that the magnetoluminescence spectra from trion and biexciton change discontinuously as the magnetic flux increases by h/2e
Dynamical Casimir effect without boundary conditions
The moving-mirror problem is microscopically formulated without invoking the
external boundary conditions. The moving mirrors are described by the quantized
matter field interacting with the photon field, forming dynamical cavity
polaritons: photons in the cavity are dressed by electrons in the moving
mirrors. The effective Hamiltonian for the polariton is derived, and
corrections to the results based on the external boundary conditions are
discussed.Comment: 12 pages, 2 figure