. . . . . . . . . .    ANM 2010     3rd International Conference on Advanced Nano Materials     12-15 September 2010 - Agadir, Morocco Back    Abstract ANMM317 COMPETITION OF SPIN AND VALLEY DEGREES OF FREEDOM IN SILICON QUANTUM DOTS FOR QUANTUM INFORMATION PROCESSING Enrico Prati Laboratorio MDM - Istituto per i Microdispositivi e i Microsistemi - CNR . In view of realizing a Silicon based quantum logic port, the interaction of the spin of confined electrons with the electromagnetic, spin and band interaction of the surrounding components of a quantum dot are discussed looking at recent experimental results. Unstrained bulk silicon is known for being an indirect bandgap semiconductor. When conduction electrons are confined close to an interface their six-fold valley degeneracy typical of bulk is splitted in a two-fold degeneracy plus a four-fold degeneracy associated to the symmetry breaking. Only the lowest valley doublet participates to transport at sufficiently low temperature. Unlike III-V compound semiconductor, the valley degeneracy is further lifted in single electron and single donor quantum dots close to the interface. The valley parity index becomes a good quantum number in competition with spin component projection along some direction. In the limit of strong coupling, the SU(4) symmetry may be achieved so valley and spin degrees of freedom are fully mixed. I discuss the competition between the spin and the valley degrees of freedom, the interaction of the spin of the electrons confined in the quantum dot with the pseudofermion constituted by the electrons of each lead, and the electromagnetic coupling of the photons used for spin manipulation with the conduction electrons of the leads. The order of magnitude of the energy and the currents associated to such interactions generally hide the electrical read out of the single spin operativity. I conclude that double dots in series may realize superior conditions in order to electrically detect single spin operativity. The novel concept of valley-blockade is introduced in the perspective of future applications. . © nanoAC . . . . . . . . . .

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