Theory of interference between electronic and phonon Raman Scattering

Abstract

A theoretical treatment is given of continuous electronic and discrete one-phonon Raman scattering for the case that the two scattering processes give rise to nearly the same Raman shifts. By using a Green's function formalism the final state interaction due to the interband electron-phonon coupling is described and it is found that the resulting line shape is similar to that of Fano's theory. A discussion is given of the frequency and the concentration dependence of the characteristic parameters.Eine theoretische Behandlung von kontinuierlicher elektronischer und diskreter Ein-Phonon-Raman-Streuung wird fur den Fall gegeben, daB die beiden Streuprozesse nLherungsweise zu den gleichen Frequenxverschiebungen fuhren. Unter Verwendung des Formalismus der Greenschen Funktionen wird die Wechselwirkung der Elementaranregungen, die in den beiden Streuprozessen angeregt werden, uber die Elektron-Phonon-Kopplung behandelt. Es wird gezeigt, daB die Linienform des Interferenzspektrums der der Fanoschen Theorie lhnlich ist. Die Frequenz-und Dotierungsabhangigkeit der charakteristischen Parameter wird diskutiert.

Fano resonances in nanoscale structures

“…Asymmetric lineshapes were also observed in Raman spectra of heavily doped semiconductors (Bechstedt and Peuker, 1975;Bell et al, 1973;Cerdeira et al, 1973a;Chandrasekhar et al, 1978;Hopfield et al, 1967;Magidson and Beserman, 2002) and high-T c superconductors (Friedl et al, 1990;Limonov et al, 1998Limonov et al, , 2000Misochko et al, 2000). Although, almost any asymmetric profile of these spectra can be fitted by the Fano formula (Aleshkin et al, 2007;Belitsky et al, 1997;Cardona, 1983;Cardona et al, 1974;Cerdeira et al, 1973b;Hase et al, 2006b;Jin and Xu, 2007;Jin et al, 2001;Menéndez and Cardona, 1985), a suitable theory for a quantitative description of these cases is still lacking.…”

Multiphonon Structure of Optical Transitions to Impurity Resonance States. The Influence of Anharmonicity

“…Band-band transitions and resonance scattering of electrons have been studied in [34, 351. Another type of resonance interaction was considered in [36] -the interaction between an electronic continuum and a single phonon mode. Recently it has been shown that the resonance impurity states preserve essential features of electron states of impurity atoms [37].…”

Interference of resonance Raman scattering by optical phonons and electronic-subband excitations inp-type modulation-doped multiple-quantum-well structures

“…(2) and (4) we have assumed that the bare twoparticle electronic Green s function is diagonal and therefore, can be written in the form (5) with E& as the electronic one-particle energy and f(e&) as the corresponding Fermi function. In Eq.…”

“…Without such an interaction the optical phonon line is broadened by an inverse phonon lifetime I The intensities of the electronic and vibronic contributions to the scattering spectrum defined in Eqs. (2) and (3) are governed by the scattering amplitudes Azz (co, ) and 8)2 (co, , co) for the pure scattering processes. During the electronic process one electron is excited from the oneparticle state lA, ') to lA, ) via intermediate states lA. "…”

“…(20), the pure electronic contribution in Eq. (2) to the scattering spectrum is given by The electronic scattering process shown in Fig. 1 and described by Eq.…”