Spin dephasing and pumping in graphene due to random spin-orbit interaction

Dugaev, V. K.; Sherman, E. Ya.; Barnaś, J.

doi:10.1103/physrevb.83.085306

Cited by 67 publications

(87 citation statements)

References 55 publications

(66 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…These limiting values of the spin Hall copnductivity are in agreement with the corresponding formulas (20) and (23). When k F R grows (keeping R constant), the conductivity initially grows with k F R and after reaching maximum it tends to the limits for k F R ≫ 1 according to the formulas (20) and (23). Note, these limits depend on R, as follows from (20) and (23).…”

Section: Rsupporting

confidence: 77%

“…This interaction includes usually a regular component, but a random term may also appear due to ripples of the graphene plane, disorder, electron-phonon coupling in the substrate, presence of adatoms, etc [16][17][18][19] . The influence of fluctuating Rashba field on spin relaxation in graphene has been analyzed for two different models of the Rashba field fluctuations 18,20 . Here we show that the spin Hall conductivity associated with such fluctuations is not universal and depends on the ratio of total momentum and spin relaxation times.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Spin Hall effect in graphene due to random Rashba field

Dyrdał

Barnaś

2012

Phys. Rev. B

Self Cite

View full text Add to dashboard Cite

Spin Hall effect due to random Rashba spin-orbit coupling in the two-dimensional honeycomb lattice of carbon atoms (graphen) is considered theoretically. Using the Green function method and diagrammatic technique we show that fluctuations of the Rashba interaction around zero average value give rise to nonzero spin Hall conductivity. Generally, the conductivity is not universal, but depends on the ratio of the total momentum and spin-flip relaxation rates.

show abstract

Section: Rsupporting

confidence: 77%

mentioning

confidence: 99%

Spin Hall effect in graphene due to random Rashba field

Dyrdał

Barnaś

2012

Phys. Rev. B

Self Cite

View full text Add to dashboard Cite

show abstract

“…Theoretical studies show that inhomogeneous spin-orbit coupling can produce both DP-like and EY-like scaling 11,26 , the relation between D and  p contains explicit density dependence due to tunable Fermi energy 27 , and sp 3 bonding can generate substantial spin relaxation 10 . Recent experiments on few layer graphene also find a variety of behaviors, with some groups reporting EY-like behavior 28 and other groups reporting DP-like behavior 14,29 .…”

mentioning

confidence: 99%

Spin Relaxation in Single-Layer Graphene with Tunable Mobility

et al. 2012

View full text Add to dashboard Cite

Abstract:Graphene is an attractive material for spintronics due to theoretical predictions of long spin lifetimes arising from low spin-orbit and hyperfine couplings. In experiments, however, spin lifetimes in single layer graphene (SLG) measured via Hanle effects are much shorter than expected theoretically. Thus, the origin of spin relaxation in SLG is a major issue for graphene spintronics. Despite extensive theoretical and experimental work addressing this question, there is still little clarity on the microscopic origin of spin relaxation. By using organic ligand-bound nanoparticles as charge reservoirs to tune mobility between 2700 and 12000 cm 2 /Vs, we successfully isolate the effect of charged impurity scattering on spin relaxation in SLG. Our results demonstrate that while charged impurities can greatly affect mobility, the spin lifetimes are not affected by charged impurity scattering. Keywords:graphene; spintronics; spin relaxation; mobility; charged impurity scattering 2 Single layer graphene (SLG) is a promising material for spintronics due to theoretical predictions of long spin lifetimes based on its low intrinsic spin-orbit and hyperfine couplings [1][2][3][4][5] . However, spin lifetimes measured in SLG spin valves are much shorter (0.05 -1.2 ns) 6-9 than predicted (100 ns -1 s) [1][2][3][4][5] . Thus, the origin of spin relaxation in SLG has become a central issue for graphene spintronics and has motivated intense theoretical and experimental studies. Theoretical studies of spin relaxation include impurity scattering 10 , ripples 5 , spin orbit domains 11,12 , and substrate effects 13 , while experimental studies have investigated contact-induced spin relaxation 7, 9, 14 , ripples 15 , band structure effects 6,14,16 , edge effects 7 and charged impurity scattering 6, 8 .However, apart from recognizing the requirement for high quality tunneling contacts to suppress contact-induced spin relaxation 9 , there is little clarity regarding the origin of spin relaxation. To address the situation, it is crucial to develop experimental techniques that systematically isolate the various microscopic sources of spin relaxation.In this work, we successfully isolate the effect of charged impurity scattering on spin relaxation in SLG by exploiting the novel tunable mobility imparted by organic ligand-bound nanoparticles on the SLG surface 17 . The nanoparticles act as charge reservoirs that freely transfer charge with graphene at room temperature. At low temperature, the frozen charge distribution on the nanoparticles results in SLG mobility ranging from 2700 to 12000 cm 2 /Vs. This approach is able to isolate the effect of charged impurity scattering on spin relaxation more clearly than previous investigations based on adatom deposition 8 . This is because depositing adatoms to the graphene surface could introduce additional effects such as short-range scattering, lattice deformation, and/or spin-orbit coupling, whereas such effects should be minimized in the current approach. Additionally, we utilize tunne...

show abstract

“…Unfortunately, spin relaxation in graphene structures has been a baffling problem [3]. While experiments in both single layer graphene (SLG) [4][5][6][7][8][9][10][11] and bilayer graphene (BLG) [7,8] yield spin lifetimes on the 100-1000 ps time scale (the highest values achieved in graphene/h-BN structures [12,13]), theories based on realistic spin-orbit coupling and transport parameters predict lifetimes on the order of microseconds [14][15][16][17][18][19][20][21][22][23][24].While the magnitudes of the spin-relaxation rates of SLG and BLG are similar, the dependence of the rates on the electron density is opposite in the two systems. In SLG the spin-relaxation rate decreases with increasing the carrier density [5][6][7][8], in BLG the spin-relaxation rate increases [7,8].…”

mentioning

confidence: 99%

Resonant Scattering by Magnetic Impurities as a Model for Spin Relaxation in Bilayer Graphene

et al. 2015

View full text Add to dashboard Cite

We propose that the observed spin relaxation in bilayer graphene is due to resonant scattering by magnetic impurities. We analyze a resonant scattering model due to adatoms on both dimer and nondimer sites, finding that only the former give narrow resonances at the charge neutrality point. Opposite to singlelayer graphene, the measured spin-relaxation rate in the graphene bilayer increases with carrier density. Although it has been commonly argued that a different mechanism must be at play for the two structures, our model explains this behavior rather naturally in terms of different broadening scales for the same underlying resonant processes. Not only do our results-using robust and first-principles inspired parameters-agree with experiment, they also predict an experimentally testable sharp decrease of the spin-relaxation rate at high carrier densities. DOI: 10.1103/PhysRevLett.115.196601 PACS numbers: 72.80.Vp, 72.25.Rb Understanding spin relaxation is essential for designing spintronics devices [1,2]. Unfortunately, spin relaxation in graphene structures has been a baffling problem [3]. While experiments in both single layer graphene (SLG) [4][5][6][7][8][9][10][11] and bilayer graphene (BLG) [7,8] yield spin lifetimes on the 100-1000 ps time scale (the highest values achieved in graphene/h-BN structures [12,13]), theories based on realistic spin-orbit coupling and transport parameters predict lifetimes on the order of microseconds [14][15][16][17][18][19][20][21][22][23][24].While the magnitudes of the spin-relaxation rates of SLG and BLG are similar, the dependence of the rates on the electron density is opposite in the two systems. In SLG the spin-relaxation rate decreases with increasing the carrier density [5][6][7][8], in BLG the spin-relaxation rate increases [7,8]. Since the diffusivity in the investigated samples decreases with increasing the electron density, it has been a common practice to assign two different mechanisms to both structures: the Elliott-Yafet mechanism [25,26] to SLG [5,6,9,10] and Dyakonov-Perel mechanism [27] to BLG [7][8][9].The main problem with that assignment is quantitative. Spin-orbit coupling in graphene [28] is too weak to yield such a small spin-relaxation time. An explicit first-principles calculation [23] predicts that one would need 0.1% of adatoms to give a 100 ps spin lifetime. Recently a new mechanism for SLG was proposed [29] (see also Ref.[30]), based on resonant scattering off local magnetic moments. It gives the observed spin-relaxation times with as little as 1 ppm of local magnetic moments and also agrees with the experimental behavior for SLG of decreasing the spinrelaxation rate with increasing electron density. Where do these local moments come from? It was theoretically predicted that adatoms such as hydrogen [31,32], but also chemisorbed organic molecules [33] can be responsible. Experimentally it was demonstrated that hydrogen adatoms indeed induce local moments [34,35], but even untreated graphene flakes were shown to exhibit 20 ppm spin 1=2 para...

show abstract

Spin dephasing and pumping in graphene due to random spin-orbit interaction

Cited by 67 publications

References 55 publications

Spin Hall effect in graphene due to random Rashba field

Spin Hall effect in graphene due to random Rashba field

Spin Relaxation in Single-Layer Graphene with Tunable Mobility

Resonant Scattering by Magnetic Impurities as a Model for Spin Relaxation in Bilayer Graphene

Contact Info

Product

Resources

About