Quantum dynamics of the Jahn-Teller complexes investigated by ultrasonic technique

Abstract

Ultrasonic technique has been used for investigation of the dynamics of the Jahn-Teller complexes in doped fluorite crystals. We use ultrasonic technique to measure temperature dependence of the real and imaginary parts of the dynamic elastic modulus of Jahn-Teller complexes. These data are used to determine the relaxation time of the distribution function over the vibronic states, which are characterized by the symmetrized deformations of the complexes. Three mechanisms of relaxation have proved to define the total relaxation time. They are thermal activation over the potential energy barriers, two-phonon mechanism, and tunneling through the barriers. The last mechanism leads to the non-zero ultrasonic attenuation and linear temperature dependence of phase velocity of the wave at low temperatures. Quantum nature of the relaxation mechanisms makes it possible to refer the Jahn-Teller effect manifestation in the mechanical properties of a crystal to the field of quantum acoustics.