20.500.12556/RUL-109777 Spektralna funkcija magnetne nečistoče Spectral function of a magnetic impurity 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. 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. Kondov pojav numeriLna renormalizacijska grupa spektralna funkcija Yu-Shiba-Rusinova stanja Kondo effect numerical renormalization group spectral function Yu-Shiba-Rusinov states true false false Slovenski jezik Angleški jezik Magistrsko delo/naloga 2019-09-08 07:45:56 2019-09-08 07:45:59 2022-08-21 03:44:25 0000-00-00 00:00:00 2019 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 98292 3368548 858.pdf 858.pdf 1 A69EC03BEC7A4C357136E3CE3770D991 ef4daf28b0d4426b5cf32b0b9aa5c941ecaa0e92cfef7c5e7e3df6eb32a7a6fe f4386731-a1b6-11eb-a523-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=121373 Fakulteta za matematiko in fiziko 0 0 0