laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Seminaire, 21 janvier 2013

Wolfgang Wensdorfer (Institut Néel, Grenoble)
Molecular Quantum Spintronics

Everyday life is full of useful magnets, solids, oxides, metals and alloys. On the contrary, molecules are most often considered as non-magnetic materials. However, recent discoveries show that molecules can bear large magnetic moments that can have a stable orientation like traditional magnets. They have therefore been called single-molecule magnets and they might be the ultimate limit for information storage. They do not only exhibit the classical macroscale property of a magnet, but also new quantum properties such as quantum tunnelling of magnetization and quantum phase interference, the properties of a microscale entity. Such quantum phenomena are advantageous for some challenging applications, e.g. molecular information storage or quantum computing.
This presentation will first resume the basics of molecular magnets and then address the field called molecular quantum spintronics, which combines the concepts of spintronics, molecular electronics and quantum computing [1]. Various research groups are currently developing low-temperature scanning tunnelling microscopes to manipulate spins in single molecules, while others are working on molecular devices (such as molecular spin-transistors, spin valves and filters, and carbon-nanotube-based devices [1]) to read and manipulate the spin state and perform basic quantum operations. The talk will discuss this - still largely unexplored - field and present few first results [2-4]. For example, we have built a novel spin-valve device [2] in which a non-magnetic molecular quantum dot, consisting of a Single-Wall Carbon Nanotube contacted with non-magnetic electrodes, is laterally coupled via supramolecular interactions to a TbPc2 molecular magnet. The localized magnetic moment of the SMM led to a magnetic field-dependent modulation of the conductance in the nanotube with magnetoresistance ratios of up to 300% below 1 K. Using a molecular spin-transistor [2], we achieved the electronic read-out of the nuclear spin of an individual metal atom embedded in a single-molecule magnet (SMM) [3]. We could show very long spin lifetimes (several tens of seconds). We also provided the first experimental evidence for a strong spin-phonon coupling between a single molecule spin and a carbon nanotube resonator [4].

[1] L. Bogani, W. Wernsdorfer, Molecular spintronics using single-molecule magnets, Nature Mat. 7, 179 (2008).
[2] M. Urdampilleta, S. Klyatskaya, M.-P. Cleuziou, M. Ruben, W. Wernsdorfer, Supramolecular Spin-Valve, Nature Mater. 10, 502-506 (2011).
[3] R. Vincent, S. Klyatskaya, M. Ruben, W. Wernsdorfer, F. Balestro, Electronic read-out of a single nuclear spin using a molecular spin-transistor, Nature 488, 357 (2012).
[4] M. Ganzhorn, S. Klyatskaya, M. Ruben, W. Wernsdorfer, Strong spin-phonon coupling between a single-molecule magnet and a carbon nanotube nanoelectromechanical system, Nature Nanotech (Feb. 2013).