Athermal photofluidization of glasses

• DOI: 10.1038/ncomms2483
• Publication Date: 2013-02-26T10:19:52Z
• Authors: G.J. Fang; J.E. Maclennan; Y. Yi; M.A. Glaser; M. Farrow; E. Korblova; D.M. Walba; T.E. Furtak; N.A. Clark
• Keywords: 01 natural sciences; 0104 chemical sciences

Azobenzene and its derivatives are among the most important organic photonic materials, with their photo-induced trans-cis isomerization leading to applications ranging from holographic data storage and photoalignment to photoactuation and nanorobotics. A key element and enduring mystery in the photophysics of azobenzenes, central to all such applications, is athermal photofluidization: illumination that produces only a sub-Kelvin increase in average temperature can reduce, by many orders of magnitude, the viscosity of an organic glassy host at temperatures more than 100 K below its thermal glass transition. Here we analyse the relaxation dynamics of a dense monolayer glass of azobenzene-based molecules to obtain a measurement of the transient local effective temperature at which a photo-isomerizing molecule attacks its orientationally confining barriers. This high temperature (T(loc)~800 K) leads directly to photofluidization, as each absorbed photon generates an event in which a local glass transition temperature is exceeded, enabling collective confining barriers to be attacked with near 100% quantum efficiency.