Université de Fribourg

Temporal mapping of photochemical reactions and molecular excited states with carbon specificity

Wang, K. ; Murahari, P. ; Yokoyama, K. ; Lord, J. S. ; Pratt, F. L. ; He, J. ; Schulz, Leander ; Willis, M. ; Anthony, J. E. ; Morley, N. A. ; Nuccio, Laura ; Misquitta, A. ; Dunstan, D. J. ; Shimomura, K. ; Watanabe, I. ; Zhang, S. ; Heathcote, P. ; Drew, Alan J.

In: Nature Materials, 2017, vol. 16, no. 4, p. 467–473

Photochemical reactions are essential to a large number of important industrial and biological processes. A method for monitoring photochemical reaction kinetics and the dynamics of molecular excitations with spatial resolution within the active molecule would allow a rigorous exploration of the pathway and mechanism of photophysical and photochemical processes. Here we demonstrate that...

Université de Fribourg

Importance of spin-orbit interaction for the electron spin relaxation in organic semiconductors

Nuccio, L. ; Willis, M. ; Schulz, Leander ; Fratini, S. ; Messina, F. ; D’Amico, M. ; Pratt, F. L. ; Lord, J. S. ; McKenzie, I. ; Loth, M. ; Purushothaman, B. ; Anthony, J. ; Heeney, M. ; Wilson, R. M. ; Hernández, I. ; Cannas, M. ; Sedlak, K. ; Kreouzis, T. ; Gillin, W. P. ; Bernhard, Christian ; Drew, Alan J.

In: Physical Review Letters, 2013, vol. 110, no. 21, p. 216602

Despite the great interest organic spintronics has recently attracted, there is only a partial understanding of the fundamental physics behind electron spin relaxation in organic semiconductors. Mechanisms based on hyperfine interaction have been demonstrated, but the role of the spin-orbit interaction remains elusive. Here, we report muon spin spectroscopy and time-resolved photoluminescence...

Université de Fribourg

Importance of intramolecular electron spin relaxation in small molecule semiconductors

Schulz, Leander ; Willis, M. ; Nuccio, L. ; Shusharov, P. ; Fratini, S. ; Pratt, F. L. ; Gillin, W. P. ; Kreouzis, T. ; Heeney, M. ; Stingelin, N. ; Stafford, C. A. ; Beesley, D. J. ; Bernhard, Christian ; Anthony, J. E. ; McKenzie, I. ; Lord, J. S. ; Drew, Alan J.

In: Physical Review B: Condensed Matter and Materials Physics, 2011, vol. 84, no. 8, p. 085209

Electron spin relaxation rate (eSR) is investigated on several organic semiconductors of different morphologies and molecular structures, using avoided level crossing muon spectroscopy as a local spin probe. We find that two functionalized acenes (polycrystalline tri(isopropyl)silyl-pentacene and amorphous 5,6,11,12- tetraphenyltetracene) exhibit eSRs with an Arrhenius-like temperature...

Université de Fribourg

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

Schulz, Leander ; Nuccio, L. ; Willis, M. ; Desai, P. ; Shakya, P. ; Kreouzis, T. ; Malik, Vivek Kumar ; Bernhard, Christian ; Pratt, F. L. ; Morley, N. A. ; Suter, A. ; Nieuwenhuys, G. J. ; Prokscha, T. ; Morenzoni, E. ; Gillin, W. P. ; Drew, Alan J.

In: Nature Materials, 2011, vol. 10, p. 39–44

Spintronics has shown a remarkable and rapid development, for example from the initial discovery of giant magnetoresistance in spin valves (Baibich, M. N. et al. Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett. 61, 2472–2475, 1988) to their ubiquity in hard-disk read heads in a relatively short time. However, the ability to fully harness electron spin as...

Université de Fribourg

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

Drew, Alan J. ; Hoppler, Julian ; Schulz, Leander ; Pratt, F. L. ; Desai, P. ; Shakya, P. ; Kreouzis, T. ; Gillin, W. P. ; Suter, A. ; Morley, N. A. ; Malik, Vivek Kumar ; Dubroka, Adam ; Kim, Kyung Wan ; Bouyanfif, Houssny ; Bourqui, Francis ; Bernhard, Christian ; Scheuermann, R. ; Nieuwenhuys, G. J. ; Prokscha, T. ; Morenzoni, E.

In: Nature Materials, 2009, vol. 8, p. 109 - 114

Electronic devices that use the spin degree of freedom hold unique prospects for future technology. The performance of these 'spintronic' devices relies heavily on the efficient transfer of spin polarization across different layers and interfaces. This complex transfer process depends on individual material properties and also, most importantly, on the structural and electronic properties of the...

Université de Fribourg

Coexistence of magnetic fluctuations and superconductivity in the pnictide high temperature superconductor SmFeAsO1-xFx measured by muon spin rotation

Drew, Alan J. ; Pratt, F. L. ; Lancaster, T. ; Blundell, S. J. ; Baker, P. J. ; Liu, R. H. ; Wu, G. ; Chen, X. H. ; Watanabe, I. ; Malik, Vivek Kumar ; Dubroka, Adam ; Kim, Kyung Wan ; Rössle, Matthias ; Bernhard, Christian

In: Physical Review Letters, 2008, vol. 101, no. 9, p. 097010

Muon spin rotation experiments were performed on the pnictide high temperature superconductor SmFeAsO1-xFx with x=0.18 and 0.3. We observed an unusual enhancement of slow spin fluctuations in the vicinity of the superconducting transition which suggests that the spin fluctuations contribute to the formation of an unconventional superconducting state. An...

Université de Fribourg

Intrinsic Mobility Limit for Anisotropic Electron Transport in Alq₃

Drew, Alan J. ; Pratt, F. L. ; Hoppler, Justin ; Schulz, Leander ; Malik, Vivek Kumar ; Morley, N. A. ; Desai, P. ; Shakya, P. ; Kreouzis, T. ; Gillin, W. P. ; Kim, Kyung Wan ; Dubroka, Adam ; Scheuermann, R.

In: Physical Review Letters, 2008, vol. 100, p. 116601

Muon spin relaxation has been used to probe the charge carrier motion in the molecular conductor Alq₃ (tris[8-hydroxy-quinoline] aluminum). At 290 K, the magnetic field dependence of the muon spin relaxation corresponds to that expected for highly anisotropic intermolecular electron hopping. Intermolecular mobility in the fast hopping direction has been found to be 0.23±0.03 cm² V⁻¹ s⁻¹...