Localized States Influence Spin Transport in Epitaxial Graphene

Abstract

We developed a spin transport model for a diffusive channel with coupled localized states that result in an effective increase of spin precession frequencies and a reduction of spin relaxation times in the system. We apply this model to Hanle spin precession measurements obtained on monolayer epitaxial graphene on SiC(0001). Combined with newly performed measurements on quasi-free-standing monolayer epitaxial graphene on SiC(0001) our analysis shows that the different values for the diffusion coefficient measured in charge and spin transport measurements on monolayer epitaxial graphene on SiC(0001) and the high values for the spin relaxation time can be explained by the influence of localized states arising from the buffer layer at the interface between the graphene and the SiC surface.

Spin relaxation in disordered graphene: Interplay between puddles and defect-induced magnetism

“…The small relaxation times observed in Ref. 7 were confirmed by other experiments with different setups [8][9][10][11][12][13][14] . A large theoretical effort has been devoted to unravel this puzzle 4,[15][16][17][18][19][20][21][22][23][24][25][26][27] and different mechanisms have been proposed for the enhanced spin relaxation, such as charge puddles 15,23,24 , impurityinduced enhancement of spin orbit interaction [17][18][19][20] and magnetic impurities 4,[21][22][23] .…”

Long-distance spin transport in high-mobility graphene on hexagonal boron nitride

“…On the other hand, τ s is theoretically predicted to range up to hundreds of nanoseconds [3]. However, observations made in the recent years by experimentalists [2,[4][5][6][7][8][9][10][11][12][13] do not match up to the high expectations set by theory. Measurements typically indicate τ s to be in the hundred picoseconds range and the discrepancy between theory and experiment and the exact relaxation mechanism remain yet unclear.…”

“…One approach to reduce the substrate roughness and screen impurities is to use epitaxial graphene on silicon carbide [12,18]. However, the presence of localized states is believed to affect spin transport in this system [13]. Alternatively, eliminating the influence of the substrate by suspending the graphene flake yields a 3 orders of magnitude increase in mobility [19,20].…”

Integrating MBE materials with graphene to induce novel spin-based phenomena

“…This is directly relevant to recent experiments concerning p z -orbital defected graphene, 55,56 but has also been discussed for epitaxial graphene on SiC. 57,58 For SiC, the graphene channel may be strongly coupled to localized states in the underlying substrate. 58 In that system, there exists a large discrepancy between D C and D S , and enhanced effective g-factors are observed.…”