Spin and valley in graphene and carbon nanotube quantum dots
28.06.2013 at 10:15
Graphene has emerged as an interesting material for coherent spin physics and spin qubits, due to the low concentration of nuclear spins and relatively weak spin-orbit coupling. However, the localization of electrons in quantum dots in graphene is a non-trivial task due to the absence of a band gap and the related effect of Klein tunneling . Among the possible solutions to this problem are electrostatically defined quantum dots in armchair graphene nanoribbons  or gapped graphene . Interestingly, the valley degeneracy present in graphene modifies the spin-orbit induced spin relaxation [4,5] as well as hyperfine interaction with C-13 nuclear spins and plays an important role in the spin-valley blockade in double quantum dots in graphene and carbon nanotubes . The exchange coupling in graphene mixes spin and valley degrees of freedom and calls for special procedures for spin-based quantum information processing .
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