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postgraduate thesis: Electronic structures of impurity and orbitalresolved vortex core states in ironselenide superconductors
Title  Electronic structures of impurity and orbitalresolved vortex core states in ironselenide superconductors 

Authors  
Issue Date  2014 
Publisher  The University of Hong Kong (Pokfulam, Hong Kong) 
Citation  Wang, Q. [王乾恩]. (2014). Electronic structures of impurity and orbitalresolved vortex core states in ironselenide superconductors. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5317029 
Abstract  We study the effect of a single nonmagnetic impurity and vortex core states in ironselenide superconductors by solving the Bogoliubovde Gennes equations selfconsistently based on a threeorbital model. Various pairing symmetry are considered in the calculation. The impurityinduced ingap bound states are found only for attractive impurity scattering potential, as in the cases of doping of Co or Ni, which is characterized by the strong particlehole asymmetry, in the nodeless d_(x^2y^2 ) wave pairing state. This property may be used to probe the pairing symmetry of ironselenide 122type superconductors. The orbitalresolved vortex core states of different pairing symmetries manifest themselves as distinguishable structures due to different behavior of the quasiparticle wavefunctions. The obtained vortices are classified by the invariant subgroups of the symmetry group of the meanfield Hamiltonian in the presence of magnetic field as isotropic s and s±wave vortices have G_5 symmetry for each orbital, whereas d_(x^2y^2 ) wave vortices show G(* )¦6 symmetry for d_xzand d_yz orbitals and G(* )¦5 symmetry for d_xy orbital. In the case of d_(x^2y^2 ) wave vortices, hybridizedpairing between d_xzand d_yz orbitals gives rise to a relative phase difference in terms of winding structures of vortices between these two orbitals and d_xy orbital, which is essentially caused by a transformation of corepresentation of G(* )¦5 and G(* )¦6 subgroup. Calculation of particle densities show common charging feature of vortices in the cases of s± and d_(x^2y^2 ) wave pairing states where the electronlike vortices are observed for d_xz and d_yz orbitals while holelike vortices for d_xyorbital. The phase difference of orbitalresolved d_(x^2y^2 ) wave vortices and their charging effects can be verified by further experimental observations. 
Degree  Doctor of Philosophy 
Subject  Ironbased superconductors 
Dept/Program  Physics 
Persistent Identifier  http://hdl.handle.net/10722/206433 
HKU Library Item ID  b5317029 
DC Field  Value  Language 

dc.contributor.author  Wang, Qianen   
dc.contributor.author  王乾恩   
dc.date.accessioned  20141031T23:15:53Z   
dc.date.available  20141031T23:15:53Z   
dc.date.issued  2014   
dc.identifier.citation  Wang, Q. [王乾恩]. (2014). Electronic structures of impurity and orbitalresolved vortex core states in ironselenide superconductors. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5317029   
dc.identifier.uri  http://hdl.handle.net/10722/206433   
dc.description.abstract  We study the effect of a single nonmagnetic impurity and vortex core states in ironselenide superconductors by solving the Bogoliubovde Gennes equations selfconsistently based on a threeorbital model. Various pairing symmetry are considered in the calculation. The impurityinduced ingap bound states are found only for attractive impurity scattering potential, as in the cases of doping of Co or Ni, which is characterized by the strong particlehole asymmetry, in the nodeless d_(x^2y^2 ) wave pairing state. This property may be used to probe the pairing symmetry of ironselenide 122type superconductors. The orbitalresolved vortex core states of different pairing symmetries manifest themselves as distinguishable structures due to different behavior of the quasiparticle wavefunctions. The obtained vortices are classified by the invariant subgroups of the symmetry group of the meanfield Hamiltonian in the presence of magnetic field as isotropic s and s±wave vortices have G_5 symmetry for each orbital, whereas d_(x^2y^2 ) wave vortices show G(* )¦6 symmetry for d_xzand d_yz orbitals and G(* )¦5 symmetry for d_xy orbital. In the case of d_(x^2y^2 ) wave vortices, hybridizedpairing between d_xzand d_yz orbitals gives rise to a relative phase difference in terms of winding structures of vortices between these two orbitals and d_xy orbital, which is essentially caused by a transformation of corepresentation of G(* )¦5 and G(* )¦6 subgroup. Calculation of particle densities show common charging feature of vortices in the cases of s± and d_(x^2y^2 ) wave pairing states where the electronlike vortices are observed for d_xz and d_yz orbitals while holelike vortices for d_xyorbital. The phase difference of orbitalresolved d_(x^2y^2 ) wave vortices and their charging effects can be verified by further experimental observations.   
dc.language  eng   
dc.publisher  The University of Hong Kong (Pokfulam, Hong Kong)   
dc.relation.ispartof  HKU Theses Online (HKUTO)   
dc.rights  This work is licensed under a Creative Commons AttributionNonCommercialNoDerivatives 4.0 International License.   
dc.rights  The author retains all proprietary rights, (such as patent rights) and the right to use in future works.   
dc.subject.lcsh  Ironbased superconductors   
dc.title  Electronic structures of impurity and orbitalresolved vortex core states in ironselenide superconductors   
dc.type  PG_Thesis   
dc.identifier.hkul  b5317029   
dc.description.thesisname  Doctor of Philosophy   
dc.description.thesislevel  Doctoral   
dc.description.thesisdiscipline  Physics   
dc.description.nature  published_or_final_version   
dc.identifier.doi  10.5353/th_b5317029   