Nonlinear optical diagnostics of phase transitions in C_(60)-TTF derivatives

摘要

A sharp-like modulation of the linear electro-optics (LEO) coefficient versus the pressure (p) and the temperature (T) has been observed for the first time. The modulation depth of the LEO (r_(222)) tensor component in the C_(60)-TTF (for He-Ne laser wavelength λ = 633 nm) was equal to about 2.6%. Varying the applied hydrostatic pressure up to 15 GPa and the temperature from 4.2 up to 25 K. We have unambiguously demonstrated that the observed effect is caused by incorporation of the TTF moiety and absent in the unsubstituted fullerenes varying the applied hydrostatic pressure up to 19 GPa and the temperature from 4.2 up to 150 K. The data obtained give a possibility for using the discovered effect for contact-less measurements of low temperatures and high pressures.