Linear response theory for a highly excited system far from equilibrium

✍ Scribed by E. Heiner

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 735 KB
• Volume: 166
• Category: Article
• ISSN: 0378-4371
• DOI: 10.1016/0378-4371(90)90077-6

✦ Synopsis

In this paper a generalization of Kubo's linear response theory is treated for systems which are driven far off equilibrium by external fields. The reduced density operator is calculated by a time-dependent projector technique in a fast moving reference frame. The response of the system with respect to a second retarded probe pulse is considered which reflects the higher complexity of the corresponding equations in comparison with Kubo's linear response theory. The response of a virtually excited exciton system to a white probe pulse is discussed for a highly excited semiconductor in the athermal stage and in the low density limit. The poles of the two-particle Green's functions contain the differences of time-dependent shifted quasi particle energies. This behavior reflects the dynamic renormalization of the band structure as the laser induced gap creation or the dynamic Stark effect.