Irreversible dynamics in incommensurate biphenyl studied by thermocycling of spectral holes - art. no. 104203

Both photochemical and nonphotochemical spectral hole burning mechanisms we re observed in the incommensurate phase III (ICIII) of chlorin-doped biphen yl. Distributions of corresponding energetic barriers for the back reaction were acquired from temperature cycling experiments. The non-photochemical mechanism is characterized by finite (unlike to glasses) but low (compared to the photochemical mechanism) threshold of 6-7 K and is interpreted as a photoinduced depinning-repinning of the incommensurate modulation wave. Hol ewidth dependence on cycling temperature up to 28 K was measured, crossing at 17 K the phase transition between two incommensurate phases in pure biph enyl. The measured irreversible hole broadening exhibits a fast (close to c ubic) increase up to 17 K and then changes abruptly to a linear in the high er-temperature incommensurate phase II, which extrapolates back to zero at T -->0 K. The results support the view that ICIII is a metastable state.