Excitonic Instabilities of Deformable Lattice - from Self-Trapping to Phase Transition

• Authors: Y. Toyozawa
• Languages of publication: EN

Abstracts

EN

The optically created exciton will be self-trapped if its coupling to phonons is strong enough, and will moreover be self-decomposed if the elec­tron and the hole couple to phonons in an opposite way. The bistability between the parity-conserved and parity-broken self-trapped excitons was observed in alkali halides. The situation is most dramatic if the bistability between the parity-broken self-trapped exciton and the ground state (with no exciton) comes into play since the electron-hole pairs may then be sponta­neously generated at every lattice site, resulting in the electronic and struc­tural phase transition. The neutral to ionic phase transition observed in a few organic charge transfer compounds under applied pressure or decreasing tem­perature can be considered as an example. Recent experiment revealed that TTF-chloranil, among others, is subject to photo-induced transient phase change over hundreds of unit cells per one photon. The dynamics of this process can be described in terms of self-trapping and self-multiplication of a photo-generated charge transfer exciton along the chain through the at­tractive dipolar interaction. This description of phase transition in terms of exciton dynamics will provide a new paradigm of materiology.

Keywords

EN

64.60.-i; 71.35.+z; 71.38.+i

Discipline

• 64.60.-i: General studies of phase transitions(see also 63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions; for critical phenomena in solid surfaces and interfaces, and in magnetism, see 68.35.Rh, and 75.40.-s, respectively)

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 1995
• Volume: 87
• Issue: 1
• Pages: 47-56

Dates

published

1995-01

Contributors

author

Y. Toyozawa

• Department of Physics, Chuo University, Kasuga 1-13-27, Bunkyo-ku, Tokyo 112, Japan

Identifiers

DOI

10.12693/APhysPolA.87.47