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Master's Dissertation
DOI
10.11606/D.76.2002.tde-15042014-102806
Document
Author
Full name
Leonardo Kleber Castelano
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2002
Supervisor
Committee
Ioriatti Júnior, Lidério Citrângulo (President)
Degani, Marcos Henrique
Marques, Gilmar Eugenio
Title in Portuguese
Auto-energia de fônons LO em super-redes delta-dopadas
Keywords in Portuguese
Excitações eletrônicas
Fônon longitudinal ótico
Super-rede
Abstract in Portuguese
Espectros Raman de super-redes δ-dopadas, na geometria de retro¬espalhamento, mostram uma estrutura na região do fônon LO que é alargada e deslocada em relação à correspondente linha observada no material intrínseco. Neste trabalho, este fenômeno é teoricamen¬te explicado através do acoplamento de um fônon LO de momento q, propagando-se ao longo da super-rede, com as excitações eletrônicas desse sistema. O deslocamento e o alargamento da linha são obtidos através do cálculo da auto-energia desse fônon, a qual pode ser expressa em termos da função resposta densidade-densidade do gás de elétrons modulado. Efeitos da interação elétron-elétron são tratados através da aproximação das fases aleatórias (RPA).
Title in English
Self-energies of LO phonons in Delta:Si:GaAs superlattices
Keywords in English
Electronic excitations
LO phonon
Super-lattices
Abstract in English
The Raman spectra of δ-doping superlattice, in backscattering ge¬ometry, show a structure in the region of the LO phonon which is broadened and shifted in comparison whit the same structure in the intrinsic material. In this work, this phenomena is interpreted as consequence of the coupling of LO xne-phonon of momentum q, along the axis of the superlattice, whit the excitations of the modulate electron gas, that exists in this system. The shift and the broadening of the phonon are calculated as the real and imagi¬nary parts of the phonon self-energy, which in turn is related to the density-density response function of modulate electron gas. Effects of electron-electron interaction are calculated within the Random Phase Approximation (RPA).
 
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Publishing Date
2014-04-16
 
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