Proučavanje supravodljivih fluktuacija i pseudoprocjepa u visokotemperaturnim supravodičima mikrovalnom metodom

doctoral thesis

• Title (english): Investigation of superconducting fluctuations and pseudogap in high temperature superconductors microwave method
• Author: Mihael Grbić
• Mentor: Miroslav Požek (mentor)
• Committee member: Slaven Barišić (predsjednik povjerenstva)
• Committee member: Miroslav Požek (član povjerenstva)
• Committee member: Mladen Prester (član povjerenstva)
• Committee member: Ivo Batistić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2011-02-02, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics
• Universal decimal classification (UDC): 53 - Physics

Abstract

U ovom radu je tehnikom mikrovalne apsorpcije proučavan doprinos fluktuacijske vodljivosti na temperaturama iznad temperature supravodljivog prijelaza (Tc) u trima porodicama kuprata - YBa2Cu3O6+x, HgBa2CuO4+δ i La2−xSrxCuO4. Iz izračunatih vrijednosti σab(c) određen je raspon temperaturnog prostiranja fluktuacija ab(c)T′. Diskutirana je ovisnost ab(c)T′ o dopiranju i kakve implikacije ono nosi obzirom na trenutna teorijska predviđanja o supravodljivim fluktuacijama i pseudoprocjepu. Za potrebe rada su izračunate raspodjele polja za modove eliptične cilindrične šupljine, raspodjela polja u beskonačno dugom pravokutnom anizotropnom uzorku, te je napravljen jednodimenzionalni numerički model za nelinearno širenje topline. Također, izrađeni su novi dijelovi eksperimentalnog postava kako bi se osigurala bolja stabilnost mjerenja, te su analizirana ranija mjerenja na uzorku Bi2Sr2CaCu2O8+δ.

Abstract (english)

We study the response of superconducting fluctuations by microwave absorption technique, above the transition temperature (Tc) in three families of cuprates - YBa2Cu3O6+x, HgBa2CuO4+δ and La2−xSrxCuO4. From the calculated values of σab(c) with and without applied magnetic field we determine the temperature span of fluctuations ab(c)T′. The doping dependence of ab(c)T′(p) and the implications of the measured data are discussed. Obtained results are compared with current theoretical and experimental findings on superconducting fluctuations and pseudogap. Within the scope of the thesis we calculated the electromagnetic field distributions of our resonating cavity, magnetic field distribution in an infinite rectangular anisotropic rod, and developed a numerical model for one−dimensional nonlinear heat propagation. Also, new parts of the measurement setup were made to ensure a better stability of the measurement process, and earlier measurements of Bi2Sr2CaCu2O8+δ were analyzed.

• Keywords: mikrovalna apsorpcija; visokotemperaturni supravodiči; dubina prodiranja; fluktuacije; vodljivost; Boltzmannova jednadžba; kuprati; modovi; rezonantna šupljina; raspodjela topline; širenje topline
• Keywords (english): microwave absorption; high temperature superconductors; penetration depth; fluctuations; conductivity; Boltzmann equation; cuprates; modes; resonating cavity; heat equation; heat distribution
• Language: croatian
• URN:NBN: urn:nbn:hr:217:392050
• Study programme: Title: Physics; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje prirodnih znanosti, polje fizika (doktor/doktorica znanosti, područje prirodnih znanosti, polje fizika)
• Type of resource: Text
• Extent: 145 str.
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-08-23 11:55:42