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Approximation methods in the polaron theory: Applications to low dimensionally confined polarons

Polaron kuramında yaklaşım yöntemleri: Düşük boyutlu polaronlara uygulamalar

  1. Tez No: 50010
  2. Yazar: R.TUĞRUL SENGER
  3. Danışmanlar: PROF.DR. ATİLLA ERÇELEBİ
  4. Tez Türü: Yüksek Lisans
  5. Konular: Fizik ve Fizik Mühendisliği, Physics and Physics Engineering
  6. Anahtar Kelimeler: Optical polaron, electron-phonon interaction, Fröhlich Hamil tonian, low dimensional structures, quantum wire, quantum dot, path integral, magneto-polaron. n, Optical polaron, electron-phonon interaction, Fröhlich Hamil tonian, low dimensional structures, quantum wire, quantum dot, path integral, magneto-polaron. n
  7. Yıl: 1996
  8. Dil: İngilizce
  9. Üniversite: İhsan Doğramacı Bilkent Üniversitesi
  10. Enstitü: Mühendislik ve Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 122

Özet

Abstract APPROXIMATION METHODS IN THE POLARON THEORY: APPLICATIONS TO LOW DIMENSIONALLY CONFINED POLARONS R. Tuğrul Senger M. S. in Physics Supervisor: Prof. Atilla Erçelebi July 1996 The polaron problem has been of interest in condensed matter physics and field theory for about half a century. Within the framework of vast variety of theoretical approximations, the bulk polaron properties have been extensively explored and fairly well understood in the literature. In the last two decades, with the impressive progress achieved in the microfabrication technology, it became possible to obtain low dimensional microstructures, in which the charge carriers are confined in one or more spatial directions. Consequently, there has appeared quite a large interest in phonon coupling-induced effects and polaronic properties of low dimensionally confined electrons. In this context, this thesis work is devoted to the study of low dimensional optical polaron properties, with the application of several different formal approaches common in the literature, such as perturbation theory, variational principles and Feynman path integral formalism. The model we adopt in thiswork consists of an electron, confined within an external potential (quantum well), and interacting via the Fröhlich Hamiltonian with the bulk LO-phonons of the relevant well material. Therefore, our primary concern is to give a clear view of only the bulk phonon effects on an electron in confined media, and we disregard all other complications that may come about from screening effects, phonon confinement, etc. Under these assumptions, we calculate the ground state energy, the effective mass, and some other quantities of polaron in several confinement geometries. We also provide a broad interpolating overview to the öne polaron problem in the overall range of electron-phonon coupling constant and in a general type of confinement, which can be conformed from one geometrical configuration to another. Another interesting theme of the polaron theory, magneto-polaron, is considered in the context of the confinement effect on the polaron, brought about by the magnetic field. A detailed analysis is given in the case, where the effect of electron-phonon coupling is dominated over by the magnetic field counterpart of the problem.

Özet (Çeviri)

Abstract APPROXIMATION METHODS IN THE POLARON THEORY: APPLICATIONS TO LOW DIMENSIONALLY CONFINED POLARONS R. Tuğrul Senger M. S. in Physics Supervisor: Prof. Atilla Erçelebi July 1996 The polaron problem has been of interest in condensed matter physics and field theory for about half a century. Within the framework of vast variety of theoretical approximations, the bulk polaron properties have been extensively explored and fairly well understood in the literature. In the last two decades, with the impressive progress achieved in the microfabrication technology, it became possible to obtain low dimensional microstructures, in which the charge carriers are confined in one or more spatial directions. Consequently, there has appeared quite a large interest in phonon coupling-induced effects and polaronic properties of low dimensionally confined electrons. In this context, this thesis work is devoted to the study of low dimensional optical polaron properties, with the application of several different formal approaches common in the literature, such as perturbation theory, variational principles and Feynman path integral formalism. The model we adopt in thiswork consists of an electron, confined within an external potential (quantum well), and interacting via the Fröhlich Hamiltonian with the bulk LO-phonons of the relevant well material. Therefore, our primary concern is to give a clear view of only the bulk phonon effects on an electron in confined media, and we disregard all other complications that may come about from screening effects, phonon confinement, etc. Under these assumptions, we calculate the ground state energy, the effective mass, and some other quantities of polaron in several confinement geometries. We also provide a broad interpolating overview to the öne polaron problem in the overall range of electron-phonon coupling constant and in a general type of confinement, which can be conformed from one geometrical configuration to another. Another interesting theme of the polaron theory, magneto-polaron, is considered in the context of the confinement effect on the polaron, brought about by the magnetic field. A detailed analysis is given in the case, where the effect of electron-phonon coupling is dominated over by the magnetic field counterpart of the problem.

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