Probing Many-Body States in Nanostructures: Pseudo-spin Resolved Transport Spectroscopy of the Kondo Effect
Probing Many-Body States in Nanostructures: Pseudo-spin Resolved Transport Spectroscopy of the Kondo Effect
Sami Amasha, Stanford University, Department of Physics
Date and time:
Thu, Feb 23, 2012 - 11:15am
Refreshments at 11:00am
Location:
LGRT 1033
Category:
Condensed Matter Seminar
Abstract:
In strongly-correlated materials, such as high-temperature
superconductors and heavy fermion compounds, electrons form many-body
states with properties different from those of non-interacting
electrons. A simpler and better understood example of electron
correlations is the Kondo effect, which describes how spins of
conduction electrons screen the spin of a localized electron that has
degenerate spin states (spin-up and spin-down in the case of a
localized spin-1/2 electron). The Kondo effect results in a many-body
ground state that produces spin correlations. Electrical transport
measurements of a single quantum dot can probe Kondo physics; however,
to directly access the spin correlations one needs spin-resolved
measurements. We address this challenge by using the orbital states
of a double quantum dot as pseudo-spin states: an electron on the
left/right dot is associated with pseudo-spin up/down. When the
energies of these pseudo-spin states are degenerate, Kondo screening
occurs. We establish a correspondence between spin Kondo in a single
dot and pseudo-spin Kondo in double dots. We use this to show that our
pseudo-spin resolved spectroscopy measurements of the Kondo state in a
double dot correspond to predictions for spin-resolved spectroscopy of
spin Kondo. Finally, we explore the interplay between orbital and spin
degeneracy in this double dot system.
Department of Physics