Nowadays, new directions in quantum spintronics aim at transposing the existing concepts and at developing alternative ones with various types of materials, from inorganic to -conjugated organic semiconductors. In this context, single molecule-magnets (SMMs) are promising candidates to be integrated in molecular spintronics devices. Such devices lead the way for the electronic detection and coherent manipulation of SMMs spin states, exploitable in quantum computation schemes. We developed for this purpose innovative multi-terminals devices based on a carbon nanotube quantum dot, laterally coupled to few SMMs or an individual SMM, as well as SMM based spin-transistor.
In the case of few SMMs coupled through supramolecular interaction to the SWNT, the localized magnetic moment of the SMM led to a magnetic field-dependent modulation of the conductance in the nanotube with magneto-resistance ratios of up to 300% at low temperatures (40 mK). We thus reported a full magnetic characterization of a single bis-phthalocyaninato terbium complex (TbPc2). In particular, we performed a detailed study of quantum tunnelling of the magnetization of the Tb electronic moment and presented a read-out technique of the Tb nuclear spin state.
In a different approach, we probed a TbPc2 SMM magnetization using a suspended carbon nanotube as a nanoelectromechanical system (NEMS) detector. We observed the presence of a quantized longitudinal stretching mode vibration in the carbon nanotube NEMS functionnalized with TbPc2 SMMs. In particular, we demonstrated the quantum mechanical nature of both systems, resulting in a strong coupling between the longitudinal stretching mode and the magnetization of an individual TbPc2 single molecule magnet grafted to the carbon nanotube’s sidewall.
Using a molecular spin-transistor obtained by electromigration, we achieved also the electronic read-out and manipulation of the nuclear spin of an individual TbPc2 SMM. We could demonstrate very long spin lifetimes (several tens of seconds). We proposed and demonstrated the possibility to perform quantum manipulation of a single nuclear spin by using an electrical field only. Since an electric field is not able to interact with the spin directly, we used an intermediate quantum mechanical process, the so called hyperfine Stark effect, to transform the electric field into an effective magnetic field two orders of magnitude higher (≈ 300 mT) than those generated using conventional nanofabrication techniques.
Molecular spintronics combines the ideas of two novel disciplines, spintronics and molecular electronics. The resulting field aims at manipulating spins and charges in electronic devices containing one or more molecules.