Spin splitting in graphene studied by means of tilted magnetic-field experiments

Kurganova, E. V.; Elferen, H. J. van; McCollam, A.; Пономаренко, Л. А.; Новоселов, К. С.; Veligura, A.; Wees, van Bart; Maan, J. C.; Zeitler, U.

doi:10.1103/physrevb.84.121407

Cited by 72 publications

(55 citation statements)

References 28 publications

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“…This procedure allows us to distinguish between the orbital effect (QHE) and pure Zeeman energy, which has to scale with the B tot value. 22,31,32 All measurements presented below were performed at a temperature of 1.3 K. The application of the magnetic field perpendicular to the sample plane leads to an increase in the resistance at the CNP, as expected for QH transport in the case of broken-symmetry states. To distinguish between the normal component and total B we perform a series of experiments keeping B n fixed and gradually increasing B tot .…”

Section: Resistance At the Cnp In Tilted Magnetic Fieldmentioning

confidence: 99%

Transport gap in suspended bilayer graphene at zero magnetic field

et al. 2012

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We report a change of three orders of magnitude in the resistance of a suspended bilayer graphene flake which varies from a few k in the high-carrier-density regime to several M around the charge neutrality point (CNP). The corresponding transport gap is 8 meV at 0.3 K. The sequence of quantum Hall plateaus appearing at filling factor ν = 2 followed by ν = 1 suggests that the observed gap is caused by the symmetry breaking of the lowest Landau level. Investigation of the gap in a tilted magnetic fields indicates that the resistance at the CNP shows a weak linear decrease for increasing total magnetic field. Those observations are in agreement with a spontaneous valley splitting at zero magnetic field followed by splitting of the spins originating from different valleys with increasing magnetic field. Both the transport gap and B field response point toward the spin-polarized layer-antiferromagnetic state as the ground state in the bilayer graphene sample. The observed nontrivial dependence of the gap value on the normal component of B suggests possible exchange mechanisms in the system.

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Section: Resistance At the Cnp In Tilted Magnetic Fieldmentioning

confidence: 99%

Transport gap in suspended bilayer graphene at zero magnetic field

et al. 2012

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“…Measurements done by Kurganova et al 20 exhibit the enhancement of the effective spin splitting leading to the effective g factor g * = 2.7 ± 0.2. Also, the enhanced effective g factor was found to be practically independent of ν.…”

Section: Fig 3 (Color Online)mentioning

confidence: 99%

“…Note that in real systems the oscillations of g * can be smoothed by a number of additional factors. The measurements of Kurganova et al 20 were performed in tilted magnetic fields and at large filling factors ν > 6. In this case the distance between the adjacent Landau levels is comparable to the Zeeman splitting which results in stronger overlap of the successive Landau levels and eventually leads to an additional smearing of g * .…”

Section: Fig 3 (Color Online)mentioning

confidence: 99%

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Interaction-induced enhancement ofgfactor in graphene

2012

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We study the effect of electron interaction on the spin splitting and the g factor in graphene in a perpendicular magnetic field using the Hartree and the Hubbard approximations within the Thomas-Fermi model. We found that the effective g factor is enhanced in comparison to its free-electron value g = 2 and oscillates as a function of the filling factor ν in the range 2 g * 4 reaching maxima at ν = 4N = 0, ± 4, ± 8, . . . and minima at ν = 4 N + 1 2 = ±2, ± 6, ± 10, . . ., with N being the Landau level index. We outline the role of charged impurities in the substrate, which are shown to suppress the oscillations of the g * factor. This effect becomes especially pronounced with the increase of the impurity concentration, when the effective g factor becomes independent of the filling factor, reaching a value of g * ≈ 2.3. A relation to the recent experiment is discussed.

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“…3f. These typically occur in relatively thick quantum wells or large fields and this behavior is surprising in graphene which is atomically thin and in pristine form has Landé g-factor ≈ 2 [23], so the Zeeman energy for B = 1 T is < 1 meV. We return to consider this point later.…”

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Rashba Interaction and Local Magnetic Moments in a Graphene-BN Heterostructure Intercalated with Au

et al. 2016

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We intercalate a van der Waals heterostructure of graphene and hexagonal Boron Nitride with Au, by encapsulation, and show that Au at the interface is two dimensional. A charge transfer upon current annealing indicates redistribution of Au and induces splitting of the graphene bandstructure. The effect of in plane magnetic field confirms that splitting is due to spin-splitting and that spin polarization is in the plane, characteristic of a Rashba interaction with magnitude approximately 25 meV. Consistent with the presence of intrinsic interfacial electric field we show that the splitting can be enhanced by an applied displacement field in dual gated samples. Giant negative magnetoresistance, up to 75%, and a field induced anomalous Hall effect at magnetic fields < 1 T are observed. These demonstrate that hybridized Au has a magnetic moment and suggests the proximity to formation of a collective magnetic phase. These effects persist close to room temperature.Spin orbit coupling in graphene is induced by hybridization with heavy metals [1]. This has been achieved by intercalation of graphene using e.g. Au, which produces a Rashba interaction ∼ 100 meV [2], and Pb [3], on metallic substrates. We intercalate Au into a heterostructure of graphene and dielectric hexagonal Boron Nitride (hBN), and report spin-splitting of the graphene bands observed in quantum oscillations on an insulating substrate, a crucial requirement for applications. The Rashba interaction is large (25 meV) for samples intercalated with 0.1 monolayers (ML) of Au, but is modulated by modest electric fields, thereby highlighting the requirement of hybridization with spin-split Au d-electrons [2]. We observe large negative magnetoresistance, up to 75%, indicating Au ions form magnetic moments and an anomalous Hall effect suggests the possible formation of a collective magnetic phase. The combination of Rashba interaction, magnetic moments and electric field control of the density, is akin to dilute magnetic semiconductors [4], and in a Dirac material opens a route toward electric field control of magnetism and engineering topological magnetic states such as the quantum anomalous Hall effect [5,6].The van der Waals interaction can create an atomically clean interface between stacked two-dimensional (2D) crystals [7]; therefore, it can be considered organizing principle for atoms or molecules at a hetero-interface [8]. Here, we use the van der Waals interaction to cleanly intercalate Au between graphene and hBN and to induce strong hybridization between graphene and Au. We intercalate graphene-hBN heterostructures by depositing 0.1-0.5 nominal ML of Au onto freshly cleaved hBN on SiO 2 in ultra high vacuum. Au decorated hBN is used as the substrate onto which a separately prepared graphene/hBN (thickness ≈ 20 nm) is transferred, the structure is illustrated in Fig. 1a. The stack is etched and metallic contacts are formed at the exposed edges of graphene [9]. Following thermal annealing the heterostructure is flat with root mean square roughness of 0....

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Spin splitting in graphene studied by means of tilted magnetic-field experiments

Cited by 72 publications

References 28 publications

Transport gap in suspended bilayer graphene at zero magnetic field

Transport gap in suspended bilayer graphene at zero magnetic field

Interaction-induced enhancement ofgfactor in graphene

Rashba Interaction and Local Magnetic Moments in a Graphene-BN Heterostructure Intercalated with Au

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