Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 31: Spin Properties of Graphene (organized by HL; with DS, MA, O, TT)

TT 31.5: Invited Talk

Tuesday, April 1, 2014, 11:45–12:15, HSZ 02

Electron spin relaxation in graphene: resonant scattering off local magnetic moments — •Jaroslav Fabian, Denis Kochan, and Martin Gmitra — Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany

Dirac electrons in graphene should have large spin relaxation time, some microseconds, due to the weak spin-orbit coupling of its itinerant electrons. Yet experiments show spin lifetimes as short as 100 ps. Traditional spin relaxation mechanisms, Elliott-Yafet and Dyakonov-Perel, seem incapable to explain such short lifetimes, even though some external influences such as hydrogen adatoms seem to induce giant local spin-orbit coupling [1] and so enhance spin-orbit induced spin flips. We believe that the culprit may instead be local paramagnetic moments due to vacancies and some adatoms. As the local moments sit on resonance sites, the spin flip is resonantly enhanced. These resonant local moments are acting as spatial spin hot spots: they may contribute little to momentum relaxation of graphene, but dominate the spin relaxation. This new mechanism explains the observed 100 ps spin lifetimes with as little as 1 ppm of local moments [2]. We acknowledge support from DFG SFB 689, SPP 1285, GRK 1579, and EC under Graphene Flagship (Contract No. CNECT-ICT-604391). [1] M. Gmitra, D. Kochan, and J. Fabian, Spin-orbit coupling in hydrogenated graphene, Phys. Rev. Lett. 110, 246602 (2013);[2] D. Kochan, M. Gmitra, and J. Fabian, Spin relaxation mechanism in graphene: resonant scattering by magnetic impurities, arXiv:1306.0230.