A common blue dye used in £5 notes could represent a promising new material for spintronic applications according to research in Nature.

Spintronic devices exploit the spin of electrons to perform functions, such as information processing, that usually rely on the movement of charge; the spins of electrons, if appropriately harnessed, might also find application in various quantum technologies.

Here the blue pigment copper phthalocyanine (CuPc) is shown to have properties that equal or rival those of more-complex molecular materials tested for spintronic applications.

Gavin Morley of Warwick’s Department of Physics worked with lead author Marc Warner from the London Centre for Nanotechnology and colleagues to demonstrate that CuPc, which is a molecular semiconductor, possesses unusually long electron spin relaxation times.

Marc Warner said: "In theory, a quantum computer can easily solve problems that a normal, classical, computer would not be able to answer in the lifetime of the universe. We just don't know how to build one yet. Our research shows that a common blue dye has more potential for quantum computing than many of the more exotic molecules that have been considered previously."

Co-author Gavin Morley, who moved to Warwick from the London Centre for Nanotechnology added “Studying thin films rather than powders means our results are relevant for real devices”.

These times determine the suitability of a material for both spintronic and quantum information applications. The spin relaxation times observed in this study suggest that CuPc could be used for quantum information processing as well as the manipulation and temporary storage of classical bits of information.

This low-cost dye can easily be processed on an industrial scale as a conventional thin film, is structurally flexible and is both chemically and thermally robust. These properties make CuPc attractive as a material for use in spintronic devices.

The full team of researchers is Marc Warner (UCL and Harvard), Salahud Din (Imperial), Igor S. Tupitsyn (University of British Columbia), Gavin W. Morley (UCL and Warwick), A. Marshall Stoneham (UCL), Jules A. Gardener (Imperial and RMD), Zhenlin Wu (Imperial), Andrew J. Fisher (UCL), Sandrine Heutz (Imperial), Christopher W. M. Kay (UCL) & Gabriel Aeppli (UCL)”. The journal reference is:

M. Warner, S. Din, I.S. Tupitsyn, G.W. Morley, A.M. Stoneham, J.A. Gardener, Z. Wu, A.J. Fisher, S. Heutz, C.W.M. Kay, and G. Aeppli, "Potential for Spin-Based Information Processing in a Thin Film Molecular Semiconductor", Nature, doi:10.1038/nature12597 (2013).

Gavin Morley can be contacted at Gavin dot Morley at warwick dot ac dot uk