Quantum phase transitions in magnetic systems: application of coupled cluster method [Elektronische Ressource] / vorgelegt von Rachid Darradi

Quantum phase transitions in magnetic systems:Application of coupled cluster methodDISSERTATIONzur Erlangung des akademischen Gradesdoctor rerum naturalium(Dr. rer. nat. )der Fakultat fur Naturwissenschaftender Otto-von-Guericke-Universitat Magdeburgvorgelegt vonDiplomphysiker Rachid DarradiMagdeburg, 27. Oktober 2008Quantum phase transitions in magnetic systems:Application of coupled cluster methodDISSERTATIONzur Erlangung des akademischen Gradesdoctor rerum naturalium(Dr. rer. nat. )genehmigt durch die Fakultat fur Naturwissenschaftender Otto-von-Guericke-Universitat Magdeburgvon Diplomphysiker Rachid Darradigeboren am 25. November 1970in Khouribga (Marokko)Gutachter: Prof. Dr. Johannes RichterPD Dr. Andreas Honeckereingereicht am: 27.10.2008verteidigt am: 26.01.2009DedicationThis work is dedicated to my family, who supported me withtheir love, care and prayers.iiiAcknowledgmentsFirst of all, I would like to express my deepest gratitude to my supervisor, Profes-sor Johannes Richter for providing me an opportunity to work with him on numberof interesting and challenging physical questions. His professional guidance, inspira-tional help, constructive criticism, and continuous support helped me to nish my worksuccessfully. Really, without his guidance this work would not have been accomplished.I would like to thank Dr. Damian Farnell and Dr. Sven Kruger for their timely help,valuable discussions and encouragement.