Spin-dependent electron tunnelling and spin relaxation were studied for a quantum dot in the regime with a filling factor between two and four. In this regime, the electronic configuration of a quantum dot undergoes transitions between a spin singlet and triplet states for an even number of electrons, and between two doublet states for an odd number of electrons. These transitions were clearly distinguished by using quantum wires as spin filtering contact leads to the dot. In addition, the temporal behaviour of electron tunnelling was studied for a quantum dot in a similar filling factor regime, using a quantum point contact as a charge sensor. Electron tunnelling through the dot in a spin singlet state could be well distinguished from that in a triplet state using the fact that the tunnelling rate was much larger for the triplet state. The difference in the tunnelling rate was also used to derive a triplet-to-singlet- state relaxation time. The obtained relaxation time agreed fairly well with that predicted by the theory of spin-orbit interaction. 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics