پديد آورنده :
زارع، محمدحسين
عنوان :
مدل كين- مل هايزنبرگ روي شبكه لانه زنبوري
گرايش تحصيلي :
فيزيك- ماده چگال
محل تحصيل :
اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك
صفحه شمار :
[هشت]،105ص.: مصور،نمودار
يادداشت :
ص.ع.به فارسي و انگليسي
استاد راهنما :
فرهاد شهبازي، فرهاد فضيله
توصيفگر ها :
نظم توسط بي نظمي , ناكامي مغناطيسي , مايع اسپيني كوانتومي , نظم جفتي , نظم بلوكي
تاريخ نمايه سازي :
18/11/93
استاد داور :
عبداله لنگري، جهانفر ابويي، مجتبي اعلائي
كد ايرانداك :
ID699 دكتري
چكيده انگليسي :
AbstractTransition metals oxides TMOs due to the presence of strong Coulomb interactions are averitable playground in condensed ma er physics for the study of novel phenomena su ashigh temperature cuprate superconductivity SC colossal magnetoresistance multiferroics and di erent ordered magnetic phases is class of materials especially 3d TMOs in whi the d orbitals are localized are a ideal systems for observing signatures of Mo insulatingbehavior In the strongly correlated limit the arge degrees of freedom freeze and the lowenergy physics of these insulators can e ectively be described by a Hamiltonian with only spindegrees of freedom e system energy can according to second order perturbation theory bereduced by the virtual hopping of electrons to neighboring sites leading to inter site spin spincorrelations e sear for new superconducting phases is o en undertaken in proximity tothe long range ordered phases as the spin uctuations play an important role in the formingof Anderson s resonant valence bond RVB states e RVB ground state is a linear combi nation of all possible singlet states whi can be formed between the spins in a system Whenthe system is doped by either holes or electrons the singlet states formed by spin uctuationsbecome mobile and the superconducting phase is borne Kane Mele proposed a model fordescribing the quantum spin Hall e ect in graphene by adding a mass term to the nearest neighbor tight binding Hamiltonian In this dissertation we study the classical and quantumphase diagram of the Kane Mele Heisenbeg model e classical diagram of the Kane Mele Heisenbeg model is obtained using three complementary methods Lu inger Tisza Variationminimization and the iterative minimization method e classical phase diagram includesthree phases with long range ordering and three disorder phases with in nitely degenerate Employing the linear spin wave analysis it is found that the quantum uctuations select a setof symmetrically equivalent in the degenerate phases In the following of the rst section ofdissertation employing exact diagonalization ED in Sz and nearest neighbor valence bond NNVB bases bond and plaque e valence bond mean eld theories We show that the disor dered regions are divided into ordered quantum states in the form of plaque e valence bondcrystal PVBC and staggered dimerized SD phases Keywords Kane Mele Heisenberg model Order by disorder Frustration antum spinliquid Staggered dimerized Plaque e order
استاد راهنما :
فرهاد شهبازي، فرهاد فضيله
استاد داور :
عبداله لنگري، جهانفر ابويي، مجتبي اعلائي
