33 research outputs found
Multiple transitions of the spin configuration in quantum dots
Single electron tunneling is studied in a many electron quantum dot in high
magnetic fields. For such a system multiple transitions of the spin
configuration are theoretically predicted. With a combination of spin blockade
and Kondo effect we are able to detect five regions with different spin
configurations. Transitions are induced with changing electron numbers.Comment: 4 pages, 5 figure
Spin Blockade in Capacitively Coupled Quantum Dots
We present transport measurements on a lateral double dot produced by
combining local anodic oxidation and electron beam lithography. We investigate
the tunability of our device and demonstrate, that we can switch between
capacitive and tunnel coupling. In the regime of capacitive coupling we observe
the phenomenon of spin blockade in a magnetic field and analyze the influence
of capacitive interdot coupling on this effect.Comment: 4 pages, 3 figure
Kondo effect in a few-electron quantum ring
A small quantum ring with less than 10 electrons was studied by transport
spectroscopy. For strong coupling to the leads a Kondo effect is observed and
used to characterize the spin structure of the system in a wide range of
magnetic fields. At small magnetic fields Aharonov-Bohm oscillations influenced
by Coulomb interaction appear. They exhibit phase jumps by at the
Coulomb-blockade resonances. Inside Coulomb-blockade valleys the Aharonov-Bohm
oscillations can also be studied due to the finite conductance caused by the
Kondo effect. Astonishingly, the maxima of the oscillations show linear shifts
with magnetic field and gate voltage.Comment: 4 pages, 4 figure