Effect of gadolinium adatoms on the transport properties of graphene

Alemani, Micol; Barfuss, Arne; Geng, Baisong; Girit, Çaǧlar; Reisenauer, P.; Crommie, Michael F.; Wang, Feng; Zettl, A.; Hellman, F.

doi:10.1103/physrevb.86.075433

Cited by 17 publications

(10 citation statements)

References 27 publications

(25 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Specific signatures of spin-orbit or magnetic scatterers are expected, whose effect should be tunable with the gate voltage [3][4][5][6]. To reach this goal, graphene has been coated with magnetic (transition metal or rare earth) atoms [7,8] as well as molecular magnets, with mixed results. Adsorbed magnetic atoms reduce graphene's mobility, with no clear concurrent magnetic signature.…”

Section: Introductionmentioning

confidence: 99%

Signature of gate-tunable magnetism in graphene grafted with Pt-porphyrins

Komatsu

Bertrand

et al. 2016

Phys. Rev. B

View full text Add to dashboard Cite

Inducing magnetism in graphene holds great promises, such as controlling the exchange interaction with a gate electrode, and generating exotic magnetic phases. Coating graphene with magnetic molecules or atoms has so far mostly lead to decreased graphene mobility. In the present work, we show that Pt-porphyrin molecules adsorbed on graphene lead both to an enhanced mobility, and to gate-dependent magnetism. We report that porphyrins can act both as donor or acceptor molecules, depending on the initial doping of the graphene sheet. The porphyrins transfer charge and ionize around the charged impurities on graphene, and, consequently, the graphene doping is decreased and its mobility is enhanced.In addition, ionized porphyrin molecules carry a magnetic moment. Using the sensitivity of mesoscopic transport to magnetism, in particular the superconducting proximity effect and conductance fluctuations, we explore the magnetic order induced in graphene by the interacting magnetic moments of the ionized porphyrin molecules.Among the signatures of magnetism, we find two-terminal-magnetoresistance fluctuations with an odd component, a tell-tale sign of time reversal symmetry breaking at zero field, that does not exist in uncoated graphene samples. When graphene is connected to superconducting electrodes, the induced magnetism leads to a gate-voltage-dependent suppression of the supercurrent, modified magnetic interference patterns, and gate-voltage-dependent magnetic hysteresis. The magnetic signatures are greatest for long superconductor/graphene/superconductor junctions, and for samples with the highest initial doping, compatible with a greater number of ionized, and thus magnetic porphyrin molecules. Our findings suggest that long-range (of the order of the coherence length, or micrometers) magnetism is induced through graphene by the ionized porphyrins' magnetic moment. This magnetic interaction is controled by the density of carriers in graphene, a tunability that could be exploited in spintronic applications.

show abstract

Section: Introductionmentioning

confidence: 99%

Signature of gate-tunable magnetism in graphene grafted with Pt-porphyrins

Komatsu

Bertrand

et al. 2016

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…Previous experiment shows that Gd introduces n doping of graphene with a doping efficiency of 0.7 electron per Gd adatom. 17 The sharp peaks of the projections are mapped to the symmetric adaptive molecular orbitals derived from the Gd-5d and -6s orbitals under the C 6v local symmetry [ Fig. S1(b)].…”

mentioning

confidence: 99%

Carrier-dependent magnetic anisotropy of Gd-adsorbed graphene

Zhou

Shao

et al. 2016

AIP Advances

View full text Add to dashboard Cite

Using first-principles calculation based on density functional theory, we study the magnetic anisotropy of Gd-adsorbed graphene and its dependence on carrier accumulation. We show that carrier accumulation not only impacts the magnitude of magnetic anisotropy but also switches its sign. Hole accumulation enhances the perpendicular anisotropy up to ∼16 meV per Gd atom, while electron accumulation switches the anisotropy from perpendicular to in-plane direction. Moreover, we find that the first order perturbation of spin-orbit coupling interaction induces a pseudo-gap at Γ for the perpendicular magnetization, which leads to the the anomalous magnetic anisotropy for the neutral composite. Our findings pave the way for magneto-electric materials based on rare-earth-decorated graphene for voltage-controlled spintronics.

show abstract

“…To date, such a prediction lacks experimental confirmation [18], despite some recent results on indium-functionalized graphene that have shown a surprising reduction of the Dirac point resistance with increasing indium density [19]. On the other hand, it is known that adatoms deposited on two-dimensional materials inevitably segregate, forming islands rather than a homogeneous distribution [20], which significantly affects doping [21,22], transport [23][24][25][26] and optical [27,28] features. The impact of adatom clustering on the formation of the QSHE remains, however, to be clarified.…”

mentioning

confidence: 99%

Multiple Quantum Phases in Graphene with Enhanced Spin-Orbit Coupling: From the Quantum Spin Hall Regime to the Spin Hall Effect and a Robust Metallic State

et al. 2014

View full text Add to dashboard Cite

We report an intriguing transition from the quantum spin Hall phase to the spin Hall effect upon segregation of thallium adatoms adsorbed onto a graphene surface. Landauer-Büttiker and Kubo-Greenwood simulations are used to access both edge and bulk transport physics in disordered thallium-functionalized graphene systems of realistic sizes. Our findings not only quantify the detrimental effects of adatom clustering in the formation of the topological state, but also provide evidence for the emergence of spin accumulation at opposite sample edges driven by spin-dependent scattering induced by thallium islands, which eventually results in a minimum bulk conductivity ∼4e 2 =h, insensitive to localization effects. Introduction.-In 2005, Kane and Mele predicted the existence of the quantum spin Hall effect (QSHE) in graphene due to intrinsic spin-orbit coupling (SOC) [1,2]. Within the QSHE, the presence of spin-orbit coupling, which can be understood as a momentum-dependent magnetic field coupling to the spin of the electron, results in the formation of chiral edge channels for spin up and spin down electron populations. The observation of the QSHE is, however, prohibited in clean graphene owing to vanishingly small intrinsic spin-orbit coupling on the order of μeV [3], but demonstrated in strong SOC materials (such as CdTe/ HgTe/CdTe quantum wells or bismuth selenide and telluride alloys), giving rise to the new exciting field of topological insulators [4][5][6][7]. Recent proposals to induce a topological phase in graphene include functionalization with heavy adatoms [8,9], covalent functionalization of the edges [10], proximity effect with topological insulators [11][12][13], or intercalation and functionalization with 5d transition metals [14,15]. In particular, the seminal theoretical study [8] by Weeks and co-workers has revealed that graphene endowed with a modest coverage of heavy adatoms (such as indium and thallium) could exhibit a substantial band gap and QSH fingerprints (detectable in transport or spectroscopic measurements). For instance, one signature of such a topological state would be a robust quantized two-terminal conductance (2e 2 =h), with an adatom density-dependent conductance plateau extending inside the bulk gap induced by SOC [8,16,17]. To date, such a prediction lacks experimental confirmation [18], despite some recent results on indiumfunctionalized graphene that have shown a surprising reduction of the Dirac point resistance with increasing indium density [19]. On the other hand, it is known that adatoms deposited on two-dimensional materials inevitably

show abstract

Effect of gadolinium adatoms on the transport properties of graphene

Cited by 17 publications

References 27 publications

Signature of gate-tunable magnetism in graphene grafted with Pt-porphyrins

Signature of gate-tunable magnetism in graphene grafted with Pt-porphyrins

Carrier-dependent magnetic anisotropy of Gd-adsorbed graphene

Multiple Quantum Phases in Graphene with Enhanced Spin-Orbit Coupling: From the Quantum Spin Hall Regime to the Spin Hall Effect and a Robust Metallic State

Contact Info

Product

Resources

About