17 research outputs found
Atmospheric Dynamics of Terrestrial Planets
The solar system presents us with a number of planetary bodies with shallow atmospheres that are sufficiently Earth-like in their form and structure to be termed “terrestrial.” These atmospheres have much in common, in having circulations that are driven primarily by heating from the Sun and radiative cooling to space, which vary markedly with latitude. The principal response to this forcing is typically in the form of a (roughly zonally symmetric) meridional overturning that transports heat vertically upward and in latitude. But even within the solar system, these planets exhibit many differences in the types of large-scale waves and instabilities that also contribute substantially to determining their respective climates. Here we argue that the study of simplified models (either numerical simulations or laboratory experiments) provides considerable insights into the likely roles of planetary size, rotation, thermal stratification, and other factors in determining the styles of global circulation and dominant waves and instability processes. We discuss the importance of a number of key dimensionless parameters, for example, the thermal Rossby and the Burger numbers as well as nondimensional measures of the frictional or radiative timescales, in defining the type of circulation regime to be expected in a prototypical planetary atmosphere subject to axisymmetric driving. These considerations help to place each of the solar system terrestrial planets into an appropriate dynamical context and also lay the foundations for predicting and understanding the climate and circulation regimes of (as yet undiscovered) Earth-like extrasolar planets. However, as recent discoveries of “super-Earth” planets around some nearby stars are beginning to reveal, this parameter space is likely to be incomplete, and other factors, such as the possibility of tidally locked rotation and tidal forcing, may also need to be taken into account for some classes of extrasolar planet
Strongly modified plasmon-matter interaction with mesoscopic quantum emitters
Semiconductor quantum dots (QDs) provide an essential link between light and
matter in emerging fields such as light-harvesting, all-solid-state quantum
communication, and quantum computing. QDs are excellent single-photon sources
and can store quantum bits for extended periods making them promising
interconnects between light and matter in integrated quantum information
networks. To this end the light-matter interaction strength must be strongly
enhanced using nanophotonic structures such as photonic crystal cavities and
waveguides or plasmonic nanowires. So far it has been assumed that QDs can be
treated just like atomic photon emitters where the spatial properties of the
wavefunction can be safely ignored. Here we demonstrate that the point-emitter
description for QDs near plasmonic nanostructures breaks down. We observe that
the QDs can excite plasmons eight times more efficiently depending on their
orientation due to their mesoscopic character. Either enhancement or suppresion
of the rate of plasmon excitation is observed depending on the geometry of the
plasmonic nanostructure in full agreement with a new theory. This discovery has
no equivalence in atomic systems and paves the way for novel nanophotonic
devices that exploit the extended size of QDs as a resource for increasing the
light-matter interaction strength.Comment: 9 pages, 4 figure