Time-dependent screening of a positive charge distribution in metals: Excitons on an ultrashort time scale

Article

关键词: ELECTRON DYNAMICS;    HOT-ELECTRONS;    SEMICONDUCTORS;    LIFETIMES;    INSULATORS;    SYSTEMS;    COPPER;    GAS;   

DOI  :  10.1103/PhysRevB.62.13464

来源: SCIE

【 摘 要 】

Experiments determining the Lifetime of excited electrons in crystalline copper reveal states which cannot be interpreted as Bloch states [S. Ogawa et at, Phys. Rev. B 55, 10 869 (1997)]. In this paper we propose a model which explains these states as transient excitonic states in metals. The physical background of transient excitons is the finite time a system needs to react to an external perturbation, in other words, the time which is needed to build up a polarization cloud. This process can be probed with modem ultrashort laser pulses. We calculate the time-dependent density-response function within the jellium model and for real Cu. From this knowledge it is possible within linear-response theory to calculate the time needed to screen a positive charge distribution and-on top of this-to determine excitonic binding energies. Our results lead to the interpretation of the experimentally detected states as transient excitonic states.

【 授权许可】

Free