Spin polarized injection into a quantum dot by means of the spatial separation of spins

We describe transport measurements on a small lateral dot involving spin po larized injection and detection. The novel layout of the lateral dot allows its electron occupation number to be reduced to 0 from 60 while maintainin g operating tunneling barriers. The spin polarized injection occurs above ( 0.4 T) due to the presence of spin resolved edge states in the two dimensio nal electron gas which form the leads to the quantum dot. We demonstrate th e consequences of spin polarized leads by focusing on two spin properties o f the quantum dot close to filling factor, v, 2. Firstly, we illustrate an alternating odd/even occupation number effect due to spin blockade through current readout at v=2. Secondly, we detect spin transitions directly at fi xed electron number in the quantum dot as the magnetic field is lowered awa y from v = 2. The experimental results are explained by a comparison to the oretical calculations of the ground states in the different regimes. The cu rrent readout process is one of the requirements of a quantum dot based spi n qubit quantum computer. (C) 2001 Elsevier Science B.V. All rights reserve d.