Dresden 2011 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 81: Graphene: Transport
HL 81.1: Vortrag
Donnerstag, 17. März 2011, 14:30–14:45, POT 151
Acoustic phonons and spin coherence in graphene nanoribbons — •Matthias Droth and Guido Burkard — University of Konstanz, 78457 Konstanz, Germany
A spintronics approach to quantum information science is considered promising due to the readily available expertise in solid state physics and possibly long coherence times [1]. We investigate a qubit implementation as real electron spin in graphene nanoribbon quantum dots. This system is particularly interesting because it allows for non-local coupling of qubits [2]. Spin coherence is determined by the coupling to nuclear spins and the lattice and the relaxation time T1 only depends on interaction with phonons. Starting from a continuum model, we derive a full phonon field theory for acoustical phonon modes in a graphene nanoribbon and at the center of the Brillouin zone. We consider fixed boundary conditions at the edges of the quasi-one-dimensional nanoribbon as well as open boundaries. In the latter case, the usual q2-dependence for out-of-plane modes in bulk is cut off at the zone center (near q=0), where we find a linear dispersion. The transverse and longitudinal sound velocities of the in-plane modes match the literature values for comparable systems [3] and, as expected, all modes approach bulk behavior for wavelengths much smaller than the ribbon width.
[1] D. Loss and D. P. DiVincenzo, Phys. Rev. A 57 (1998).
[2] B. Trauzettel et al., Nature Physics 3 (2007).
[3] L. A. Falkovsky, Phys. Lett. A 372 (2008).