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Electronic Structure Calculation of (Sr,Ca)2Ru04 By GW Approximation

Hooshmand Quarebagh, Zahra | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40774 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Akhavan, Mohammad
  7. Abstract:
  8. In this thesis, we have studied systems called Ruthenates, which are common in possessing Ru element in their chemical compounds. Ruthenates are a group of transition metal oxides which have attracted so attention, especially in last years duo to their rich phase diagram which shows different orbital, charge and spin orderings.They cover a vast range of materials properties, from a Superconductor to Mott Hubbard insulator, from a paramagnetic metal to an antiferromanetic insulator. In these systems, substituting a covalent atom with structure base, leads to a vast variety changing, not only in electronic properties but also in magnetic and structural ones: Although Sr"RuO£ is a ferromagnetic superconductor, Ca"RuO£ is an aniferromagnetic Mott insulator. Besides, different concentration of same base leads completely in different electronic properties. For example, while CaRuOr is a metal, Ca"RuO£ is a Mott insulator. These kind of properties make these systems overally as strongly correlated systems which are difficult to study with Fermi liquid base theories like DFT. We have concentrated on two members of Ruthenates: Ca"RuO£ and Sr"RuO£. We have studied both systems by many body perturbation theory called GW approximation. In this approximation, an effective potential of quasiparticles is replaced by bare electrons potential. The most central quantity of this method is electrons self energy and green functions which then posses electrons dynamical properties information. We then, have studied some useful characters of system such as: effective mass, dielectric function, Plasmon frequency, spectral function, etc
  9. Keywords:
  10. Electron Structure ; Strongly Correlated Electron Systems ; Ruthenates ; GW Approximation ; Transition Metal Oxides ; Many Body Approximation

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