magistrsko delo
Abstract
Obravnavam magnetno nečistočo, sklopljeno s kovinsko oz. superprevodno podlago. Sistem opišem s Kondovim modelom. Formuliran je problem, nato pa je predstavljena metoda numerične renormalizacijske grupe, ki je standardna numerična metoda na tem področju. Uporabil sem jo za izračun spektralne funkcije nečistoče, ki ustreza lokalni gostoti stanj. V njej se pojavi resonančni vrh pri Fermijevi energiji, ki je tipičen za Kondov pojav. V primeru s kovinsko podlago nas zanima, kako se vrh obnaša v odvisnosti od premika energijskih nivojev nečistoče. Opazimo, da se Kondov pojav zaduši, če nečistočo zmotimo z motnjo, ki je po velikosti primerljiva s Kondovo energijsko skalo. V primeru s superprevodno podlago sem se osredotočil na diskretna stanja, ki jih opazimo v superprevodni reži. Položaj in razcep vrhov razložim s pomočjo diagramov energij najnižjih v zbuditev sistema.
Keywords
fizika kondenzirane snovi;magnetne nečistoče;Kondov pojav;numerična renormalizacijska grupa;
Data
Language: |
Slovenian |
Year of publishing: |
2019 |
Typology: |
2.09 - Master's Thesis |
Organization: |
UL FMF - Faculty of Mathematics and Physics |
Publisher: |
[L. Pavešić] |
UDC: |
538.9 |
COBISS: |
3368548
|
Views: |
758 |
Downloads: |
265 |
Average score: |
0 (0 votes) |
Metadata: |
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Other data
Secondary language: |
English |
Secondary title: |
Spectral function of a magnetic impurity |
Secondary abstract: |
The problem of a magnetic impurity, coupled to a metal or a superconducting bath is treated. The system is described using the Kondo model. We formulate the problem, and present the numerical renormalization group method, a standard numerical method in the field. It is employed for calculations of the impurity spectral function, which corresponds to a local density of states. We observe a resonance peak at the Fermi level, which turns out to be typical for the Kondo effect. In the case of the metal bath, we are mostly interested in the behaviour of the resonance peak and its dependence on the impurity energy levels. The Kondo effect fades when we disturb the impurity with a perturbation, comparable in strenght to the coupling energy scale. In the superconducting bath case, focus is on the discrete states that appear in the superconducting gap. Position and splitting of the subgap states is understood using the energy level diagrams of the lowest laying excitations of the system. |
Secondary keywords: |
condensed matter physics;magnetic impurities;Kondo effect;numerical renormalization group; |
Type (COBISS): |
Master's thesis/paper |
Study programme: |
0 |
Embargo end date (OpenAIRE): |
1970-01-01 |
Thesis comment: |
Univ. v Ljubljani, Fak. za matematiko in fiziko, Oddelek za fiziko |
Pages: |
68 str. |
ID: |
11218588 |