1,459 research outputs found
Aharonov-Bohm effect for excitons in a semiconductor quantum ring dressed by circularly polarized light
We show theoretically that the strong coupling of circularly polarized
photons to an exciton in ring-like semiconductor nanostructures results in
physical nonequivalence of clockwise and counterclockwise exciton rotations in
the ring. As a consequence, the stationary energy splitting of exciton states
corresponding to these mutually opposite rotations appears. This excitonic
Aharonov-Bohm effect depends on the intensity and frequency of the circularly
polarized field and can be detected in state-of-the-art optical experiments.Comment: Published versio
Cool Customers in the Stellar Graveyard I: Limits to Extrasolar Planets Around the White Dwarf G29-38
We present high contrast images of the hydrogen white dwarf G 29-38 taken in
the near infrared with the Hubble Space Telescope and the Gemini North
Telescope as part of a high contrast imaging search for substellar objects in
orbit around nearby white dwarfs.
We review the current limits on planetary companions for G29-38, the only
nearby white dwarf with an infrared excess due to a dust disk. We add our
recent observations to these limits to produce extremely tight constraints on
the types of possible companions that could be present. No objects 6
M are detected in our data at projected separations 12 AU, and no
objects 16 M are detected for separations from 3 to 12 AU, assuming
a total system age of 1 Gyr. Limits for companions at separations 3 AU come
from a combination of 2MASS photometry and previous studies of G29-38's
pulsations. Our imaging with Gemini cannot confirm a tentative claim for the
presence of a low mass brown dwarf. These observations demonstrate that a
careful combination of several techniques can probe nearby white dwarfs for
large planets and low mass brown dwarfs.Comment: 20 pages, 4 figures, Accepted to Ap
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