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Spin and valley in graphene and carbon nanotube quantum dots

Guido Burkard (University of Constance, Germany)

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 [1]. Among the possible solutions to this problem are electrostatically defined quantum dots in armchair graphene nanoribbons [2] or gapped graphene [3]. 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 [6]. The exchange coupling in graphene mixes spin and valley degrees of freedom and calls for special procedures for spin-based quantum information processing [7].

[1] M. I. Katsnelson, K. S. Novoselov, A. K. Geim, Nature Phys. 2, 620 (2006).
[2] B. Trauzettel, D. Bulaev, D. Loss, and GB, Nature Phys. 3, 192 (2007).
[3] P. Recher, J. Nilsson, GB, and B. Trauzettel, Phys. Rev. B 79, 085407 (2009).
[4] P. R. Struck and GB, Phys. Rev. B 82, 125401 (2010).
[5] M. Droth and GB, Phys. Rev. B 84, 155404 (2011); ibid. 87, 205432 (2013).
[6] A. Palyi and GB, Phys. Rev. B 80, 201404 (2009); ibid. 82, 155424 (2010).
[7] N. Rohling and GB, New Journal of Physics 14, 083008 (2012).

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