Abstract
Controlling the dynamics of spins on surfaces is pivotal to the design of spintronic1 and quantum computing2 devices. Proposed schemes involve the interaction of spins with graphene to enable surface-state spintronics3,4, and electrical spin-manipulation4-11. However, the influence of the graphene environment on the spin systems has yet to be unraveled12. Here we explore the spin-graphene interaction by studying the classical and quantum dynamics of molecular magnets13 on graphene. While the static spin response remains unaltered, the quantum spin dynamics and associated selection rules are profoundly modulated. The couplings to graphene phonons, to other spins, and to Dirac fermions are quantified using a newly-developed model. Coupling to Dirac electrons introduces a dominant quantum-relaxation channel that, by driving the spins over Villain’s threshold, gives rise to fully-coherent, resonant spin tunneling. Our findings provide fundamental insight into the interaction between spins and graphene, establishing the basis for electrical spin-manipulation in graphene nanodevices.
Highlights
Controlling the dynamics of spins on surfaces is pivotal to the design of spintronic[1] and quantum computing[2] devices
We exploit the exceptionally clean[13] magnetic features of single-molecule-magnets (SMMs) to explore how spins interact with graphene substrates
The graphene–SMM hybrids are obtained by non-covalent grafting of [Fe4(L)2(dpm)6], (Hdpm=dipivaloylmethane and H3L=2-hydroxymethyl-2-(4-(pyren-1-yl)-butoxy)methylpropane1,3-diol, Fig. 1a; ref. 20) via solution-based assembly on exfoliated graphene sheets
Summary
Christian Cervetti1*, Angelo Rettori[2], Maria Gloria Pini[3], Andrea Cornia[4], Ana Repollés[5], Fernando Luis[5], Martin Dressel[1], Stephan Rauschenbach[6], Klaus Kern[6,7], Marko Burghard[6] and Lapo Bogani1,8*. Carbon-based spintronics offers the means to manipulate localized spins in the close proximity of a carbon nanotube[14,15,16] or graphene sheet[4,5,6,7,8,9,10,11] This task requires understanding and tuning the interaction between the components, to minimize quantumdecoherence[16], and to enable spin manipulation[17], for example, by controlling either the magnetic anisotropy[18] or the electronic coupling[5,19]. Raman spectra (Fig. 1d) exhibit only a small up-shift of the graphene G band by ∼4 cm−1 after functionalization, indicating slight p-type doping[21] This conclusion is supported by the small positive shift of the charge neutrality point observed in the resistance versus gate voltage curves (Fig. 1e,f), corresponding to a chargetransfer of only 0.08 e− per SMM. Campi 183, I-41125 Modena, Italy. 5Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, C/ Pedro Cerbuna 12, E-50009 Zaragoza, Spain. 6Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany. 7Institut de Physique de la Matière Condensée, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland. 8Department of Materials, University of Oxford, 16 Parks Road, Oxford OX1 3PH, UK
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