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SYTG: Symposium Transport in Graphene

SYTG 1: Symposium: Transport in Graphene

SYTG 1.3: Hauptvortrag

Dienstag, 24. März 2009, 15:00–15:30, BAR SCHÖ

Spins and valley-spins in graphene nanostructures — •Inanc Adagideli — Universitaet Regensburg

In this talk, I will discuss spin and valley-spin dependent transport in graphene nanostructures particularly nanoribbons and quantum dots. First, I will focus on graphene nanoribbons and show how the states localized at their edges get magnetized and can be used for spin injection [1]. Furthermore, nanoribbons with rough edges exhibit spin conductance fluctuations with a universal value of 0.4 e/4π, when the localization length is comparable to the length of the ribbon. Next, I will focus on the graphene quantum dots and discuss the universalities featured by their spectra and conductance and how these properties depend on their edges[2]. Particularly if the confinement is due to abrupt lattice termination, these properties are well described by the standard orthogonal (unitary in the presence of magnetic field) ensemble of random matrix theory. However, if the confinement is due to a smooth mass boundary, the Hamiltonian is block diagonal in the valley degree of freedom and expected to feature time reversal symmetry breaking in the absence of magnetic fields. Although the effect of this structure is clearly visible in the conductance of open dots, it is suppressed in the spectral statistics of closed dots. I will conclude by describing a semiclassical theory of quantum transport in graphene nanostructures that qualitatively describes the spin and valley-spin dynamics as well as their universal effects on the quantum transport and energy spectra.

[1] M. Wimmer et al., Phys. Rev. Lett. 100, 177207 (2008)

[2] J. Wurm et al., arXiv:0808.1008v1