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On the Nonstationary Processes in Exciton Systems
Author(s) -
Hadžiselimović E. A.,
Marinković M. M.,
Tošić B. S.
Publication year - 1980
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221000206
Subject(s) - exciton , excitation , annihilation , physics , dissipation , operator (biology) , statistical physics , correlation function (quantum field theory) , lattice (music) , creation and annihilation operators , stationary state , sum rule in quantum mechanics , quantum mechanics , chemistry , quantum , biochemistry , repressor , transcription factor , acoustics , gene , quantum chromodynamics , dielectric
In consequence of the nonconservation of excitons, the excitation number operator as well as the exciton pair creation and annihilation operators are expressed as functions of time and of the corresponding stationary operators. The nonstationary pair correlation processes and the nonstationary excitation density fluctuation processes are analysed using the nonstationary operators. It is found that the nonstationary pair correlations are characterized by a specific kind of dissipation that is linearly proportional with time. In contradistinction to stationary processes, the corresponding nonstationary ones, lead to elementary excitations having a double energy: E (nonstationary) = 2 E (stationary). It is shown that in contrast to exciton density fluctuations, pair correlations have a tendency of localization related to a lattice point. It is also shown that the exciton non‐statinoary pair correlations are in many respect similar to the density fluctuations that take place in the crystal due to a near slow neutron passage. Finally, a general method for the evaluation of the correlation function, applicable even in the case when the Green's function has a n ‐th order pole, is developed in the Appendix.