Intrinsic and Rashba spin-orbit interactions in graphene sheets

Min, Hongki; Hill, Jason E.; Sinitsyn, Nikolai A.; Sahu, Bhagawan; Kleinman, Leonard; MacDonald, Allan H.

doi:10.1103/physrevb.74.165310

Cited by 1,054 publications

(915 citation statements)

References 23 publications

Supporting

Mentioning

875

Contrasting

Unclassified

Order By: Relevance

“…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.…”

Section: Introductionmentioning

confidence: 80%

See 1 more Smart Citation

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

Section: Introductionmentioning

confidence: 80%

“…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] .…”

mentioning

confidence: 99%

Spin Relaxation in Single-Layer Graphene with Tunable Mobility

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Whenever mirror symmetry is broken, due to application of an external off-plane electric field, or due to interaction with the substrate, another spin orbit coupling arises known as the Rashba Hamiltonian 19,22 :…”

Section: B Spin Dependent Termsmentioning

confidence: 99%

Edge states in graphene-like systems

2015

View full text Add to dashboard Cite

The edges of graphene and graphene like systems can host localized states with evanescent wave function with properties radically different from those of the Dirac electrons in bulk. This happens in a variety of situations, that are reviewed here. First, zigzag edges host a set of localized non dispersive state at the Dirac energy. At half filling, it is expected that these states are prone to ferromagnetic instability, causing a very interesting type of edge ferromagnetism. Second, graphene under the influence of external perturbations can host a variety of topological insulating phases, including the conventional Quantum Hall effect, the Quantum Anomalous Hall (QAH) and the Quantum Spin Hall phase, in all of which phases conduction can only take place through topologically protected edge states. Here we provide an unified vision of the properties of all these edge states, examined under the light of the same one orbital tight-binding model. We consider the combined action of interactions, spin orbit coupling and magnetic field, which produces a wealth of different physical phenomena. We briefly address what has been actually observed experimentally.

show abstract

“…Second, the energy gap between electronand hole-like Landau levels must be small enough to be invertible by the Zeeman splitting. Both of these conditions are met in graphene, a gapless semimetal with very weak spin-orbit coupling 18 . The graphene LL structure is characterized by the existence of a fourfold spin-and valley-degenerate LL at zero energy(zLL) 19 .…”

mentioning

confidence: 99%

Tunable symmetry breaking and helical edge transport in a graphene quantum spin Hall state

Young

Sanchez-Yamagishi

Hunt

et al. 2013

Nature

290

349

View full text Add to dashboard Cite

Low-dimensional electronic systems have traditionally been obtained by electrostatically confining electrons, either in heterostructures or in intrinsically nanoscale materials such as single molecules, nanowires, and graphene. Recently, a new paradigm has emerged with the advent of symmetry-protected surface states on the boundary of topological insulators, enabling the creation of electronic systems with novel properties. For example, time reversal symmetry (TRS) endows the massless charge carriers on the surface of a three-dimensional topological insulator with helicity, locking the orientation of their spin relative to their momentum 1,2 . Weakly breaking this symmetry generates a gap on the surface, 3 resulting in charge carriers with finite effective mass and exotic spin textures 4 . Analogous manipulations of the one-dimensional boundary states of a two-dimensional topological insulator are also possible, but have yet to be observed in the leading candidate materials 5,6 . Here, we demonstrate experimentally that charge neutral monolayer graphene displays a new type of quantum spin Hall (QSH) effect 7,8 , previously thought to exist only in time reversal invariant topological insulators 5,9-11 , when it is subjected to a very large magnetic field angled with respect to the graphene plane. Unlike in the TRS case 5,9,10 , the QSH presented here is protected by a spin-rotation symmetry that emerges as electron spins in a half-filled Landau level are polarized by the large in-plane magnetic field. The properties of the resulting helical edge states can be modulated by balancing the applied field against an intrinsic antiferromagnetic instability [12][13][14] , which tends to spontaneously break the spin-rotation symmetry. In the resulting canted antiferromagnetic (CAF) state, we observe transport signatures of gapped edge states, which constitute a new kind of one-dimensional electronic system with tunable band gap and associated spin-texture 15 .In the integer quantum Hall effect, the topology of the bulk Landau level (LL) energy bands 16 requires the existence of gapless edge states at any interface with the vacuum. The metrological precision of the Hall quantization can be traced to the inability of these edge states to backscatter due to the physical separation of modes with opposite momentum by the insulating sample bulk 17 . In contrast, counterpropagating boundary states in a symmetry-protected topological (SPT) insulator coexist spatially but are prevented from backscattering by a symmetry of the experimental system 1,2 . The local symmetry that protects transport in SPT surface states is unlikely to be as robust as the inherently nonlocal physical separation that protects the quantum Hall effect. However, it enables the creation of new electronic systems in which momentum and some quantum number such as spin are coupled, potentially leading to devices with new functionality. Most experimentally realized SPT phases are based on TRS, with counterpropagating states protected from intermixing by the Kram...

show abstract

Intrinsic and Rashba spin-orbit interactions in graphene sheets

Cited by 1,054 publications

References 23 publications

Spin Relaxation in Single-Layer Graphene with Tunable Mobility

Spin Relaxation in Single-Layer Graphene with Tunable Mobility

Edge states in graphene-like systems

Tunable symmetry breaking and helical edge transport in a graphene quantum spin Hall state

Contact Info

Product

Resources

About