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Superconductivity problems with multiple Ginzburg-Landau order parameters
Thesis (MSc)--Stellenbosch University, 2011.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2011
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| _version_ | 1867614091440291840 |
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| access_status_str | Open Access |
| author | Geyer, Jani |
| author2 | Kastner, Michael |
| author_browse | Geyer, Jani Kastner, Michael |
| author_facet | Kastner, Michael Geyer, Jani |
| author_sort | Geyer, Jani |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2011. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/17916 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:46:31.699Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2011 |
| publishDateRange | 2011 |
| publishDateSort | 2011 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/17916 Superconductivity problems with multiple Ginzburg-Landau order parameters Geyer, Jani Kastner, Michael Schmalian, Jorg Stellenbosch University. Faculty of Science. Dept. of Physics. Superconductivity Ginzburg-Landau theory Anti-Ferromagnetism Dissertations -- Physics Theses -- Physics Thesis (MSc)--Stellenbosch University, 2011. ENGLISH ABSTRACT: Two problems in the field of materials-based condensed matter physics, specifically in the field of superconductivity, are studied theoretically. In both problems, where each is of current exper- imental interest, an extension of Ginzburg-Landau theory is used to describe a physical system, with focus on the energy associated to the interface(s) occurring in the respective systems. The first physical system under consideration is that of a two-band superconductor. Using Ginzburg-Landau theory for two-band superconductors, the interface energy ¾s between normal and superconducting states coexisting at the thermodynamic critical magnetic field is determined. From the theoretical and numerical analysis of the interface energy, it is found that close to the transition temperature, where the Ginzburg-Landau theory is applicable, the two-band problem maps onto an effective single band problem. This finding puts into question the possibility of intermediate, so called type-1.5 superconductivity, in the regime where the Ginzburg-Landau theory applies. The second physical system is that of a system with competing superconductivity and anti- ferromagnetism. From Ginzburg-Landau theory for such competing systems in a thermodynamic critical magnetic field, it is shown that two possible interfaces can occur: an interface between a pure anti-ferromagnetic state and a pure superconducting state; and an interface between a state with coexisting superconductivity and anti-ferromagnetism and a pure anti-ferromagnetic state. The energy associated to both these interfaces is analysed theoretically and numerically from which the boundary between type-I and type-II superconductivity is obtained for certain specific cases. AFRIKAANSE OPSOMMING: Twee probleme in die veld van materiaal-gebaseerde gekondenseerde materie fisika, spesifiek in die veld van supergeleiding, word teoreties bestudeer. In beide probleme, albei tans van eksper- imentele belang, word ’n fisiese sisteem beskryf deur ’n uitbreiding van enkel-band Ginzburg- Landau teorie, met fokus op die energie geassosieer met die koppelvlak(ke) wat in die onderskeie sisteme aangetref word. Die eerste fisiese sisteem wat beskou word is die van ’n twee-band supergeleier. Deur van Ginzburg-Landau teorie vir twee-band supergeleiers gebruik te maak, word die koppelvlak energie ¾s tussen die gelyktydig bestaande normaal- en supergeleidende toestand in die termodinamiese kritieke magneetveld bepaal. Deur beide teoretiese en numeriese analieses word bepaal dat na aan die oorgangstemperatuur, waar Ginzburg-Landau teorie geldig is, die twee-band probleem op ’n effektiewe een-band probleem afbeeld. Hierdie bevinding bevraagteken dus die moontlikheid van onkonvensionele, of sogenaamde tipe-1.5 supergeleiding, vir gevalle waar Ginzburg-Landau teorie geldig is. Die tweede fisiese siteem wat beskou word is ’n sisteem met kompeterende supergeleiding en anti-ferromagnetisme. Met behulp van Ginzburg-Landau teorie vir sulke sisteme in ’n termod- inamiese kritiese magneetveld word gewys dat daar twee moontlike koppelvlakke kan ontstaan: ’n koppelvlak tussen ’n uitsluitlik anti-ferromagnetiese toestand en ’n uitsluitlik supergeleidende toestand; sowel as ’n koppelvlak tussen ’n uitsluitlik anti-ferromagnetiese toestand en ’n toes- tand van beide supergeleiding en anti-ferromagnetisme. Die energie geassosieer met beide hierdie koppelvlakke word teoreties en numeries geanaliseer wat lei tot ’n beskrywing van die grenslyn tussen tipe-I en tipe-II supergeleiding in sekere spesifieke gevalle. 2011-11-22T14:28:00Z 2011-12-05T13:11:03Z 2011-11-22T14:28:00Z 2011-12-05T13:11:03Z 2011-12 Thesis http://hdl.handle.net/10019.1/17916 en_ZA Stellenbosch University 99 p. : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Superconductivity Ginzburg-Landau theory Anti-Ferromagnetism Dissertations -- Physics Theses -- Physics Geyer, Jani Superconductivity problems with multiple Ginzburg-Landau order parameters |
| title | Superconductivity problems with multiple Ginzburg-Landau order parameters |
| title_full | Superconductivity problems with multiple Ginzburg-Landau order parameters |
| title_fullStr | Superconductivity problems with multiple Ginzburg-Landau order parameters |
| title_full_unstemmed | Superconductivity problems with multiple Ginzburg-Landau order parameters |
| title_short | Superconductivity problems with multiple Ginzburg-Landau order parameters |
| title_sort | superconductivity problems with multiple ginzburg landau order parameters |
| topic | Superconductivity Ginzburg-Landau theory Anti-Ferromagnetism Dissertations -- Physics Theses -- Physics |
| url | http://hdl.handle.net/10019.1/17916 |
| work_keys_str_mv | AT geyerjani superconductivityproblemswithmultipleginzburglandauorderparameters |