Condensed Matter and Materials Physics(DCMMP)
Physique de la matière condensée et des matériaux (DPMCM)
Erik SORENSEN
McMaster University
Kondo Effect and Persistent Currents in Quantum Dot Systems
Quantum dots can be created not only in semiconductors but also in carbon nanotubes by artificially introducing kinks. Transport through such a system shows a very rich structure. In some cases transport is blocked due to charging effects, the so-called Coulomb blockade. Most interestingly, this blockade phenomenon is sometimes overcome by an effect entirely due to the electron spin, the famous Kondo effect. This effect is most prominently present when the behavior of the quantum dot can be modelled as a single magnetic impurity and is due to the formation of a cloud of electrons screening the magnetic impurity. A neat way of studying this phenomenon is by measuring the persistent current induced by a magnetic field when the system forms a closed ring. The induced persistent current will be strongly modified by the magnetic impurity. The sizable cloud of electrons trying to screen the magnetic impurity will give rise to specific finite-size corrections to the persistent current in such a mesoscopic systems. Calculations of transport properties are notoriously difficult and after an introduction to the underlying physics I will present numerical results from large-scale parallelized density matrix renormalization group and exact diagonalization studies of these systems, obtained using the SHARCnet facilities at McMaster.