Date:
Monday March 21, 2011
Time: 13:00
Place: ETH Science City, HPF G 6
Host:
Tilman Esslinger
Quantum
transport with matter-waves
Philippe Bouyer
Institut d'Optique, Palaiseau, France
The
transport of quantum particles in non ideal material media (eg the conduction of
electrons in an imperfect crystal) is strongly affected by scattering from
impurities of the medium. Even for a weak disorder, semi-classical theories,
such as those based on the Boltzmann equation for matter-waves scattering from
the impurities, often fail to describe transport properties and full quantum
approaches are necessary. The properties of the quantum systems are of
fundamental interest as they show intriguing and non-intuitive phenomena that
are not yet fully understood such as Anderson localization, percolation,
disorder-driven quantum phase transitions and the corresponding Bose-glass or
spin-glass phases. Understanding quantum transport in amorphous solids is one
of the main issues in this context, related to electric and thermal
conductivities.
Ultracold atomic gases can now
be considered to revisit the problem of quantum conductivity and quantum
transport under unique control possibilities. Dilute atomic Bose-Einstein
condensates (BEC) and degenerate Fermi gases (DFG) are produced routinely
taking advantage of the recent progress in cooling and trapping of neutral
atoms. Transport has been widely investigated in controlled potentials with no
defects, for instance periodic potentials (optical lattices). Controlled
disordered potentials can also be produced with various techniques such as the
use of magnetic traps
designed
on atomic chips with rough wires, the use of localized impurity atoms, the use
of radio-frequency fields or the use of optical potentials. This recently lead
to the observation of the Anderson Localization of a BEC and
the
measurement of the diffusion coefficient of a 2D gas in the presence of
disorder. I will also discuss the recent development towards the observation of
AL in 3D with matter-waves.