Electronic structure of a conventional superconductor in the vicinity of a single, iso-
lated magnetic impurity has been probed experimentally with scanning tunneling
spectroscopy by Yazdani et al.. Motivated by their experiment, we study the ef-
fects of a single magnetic impurity on superconductivity by means of the mean-¯eld
Bogoliubov-de Gennes theory. The Bogoliubov-de Gennes equations are solved di-
rectly and numerically, utilizing parallel computation on a CFI-founded 128-CPU
Beowulf-class PC cluster here at the University of Saskatchewan. As a preliminary
study, we also examine the electronic structure around a magnetic vortex. The local
magnetic field around a vortex breaks up Cooper pairs and suppresses superconduc-
tivity locally. Quasiparticle excitations are created and bound in the vortex core area
due to repeated Andreev scattering. A magnetic impurity tends to align the spins of
the neighboring electrons and break up Cooper pairs, and has similar effects of lo-
cally suppressing superconductivity. A striking difference, however, from the vortex
problem is that around a magnetic impurity there is particle-hole asymmetry in the
tunneling conductance. This is due to different probability amplitudes in the spin-up
branch and the spin-down branch of quasiparticle excitations. Furthermore, for the
spin potential strength larger than a certain critical value, the nature of quasiparticle
excitations is changed dramatically. Within a model of classical spin, we propose an
explanation of the measured tunneling conductance of the experiment. This work
is significant in that it gives us insight into superconductivity and magnetism{two
complementary manifestation of strong electron correlations.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-01062009-123150 |
| Date | 12 January 2009 |
| Creators | Pan, Sushan |
| Contributors | Tanaka, Kaori, Soteros, Chris, Hussey, Glenn C., Gap Soo, Chang, Dick, Rainer, Xiao, Chijin |
| Publisher | University of Saskatchewan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-01062009-123150/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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