Preklopi med topološkima fazama v neurejenem Su-Schrieffer-Heegerjevem modelu

magistrsko delo

Andrej Kolar-Požun (Author), Tomaž Rejec (Mentor), Lara Ulčakar (Co-mentor)

Abstract

V delu obravnavamo neurejen Su-Schrieffer-Heegerjev model. V takem sistemu lahko med topološkima fazama prehajamo tudi s spreminjanjem jakosti nereda. Kritična točka tega prehoda je zaznamovana z delokalizacijo stanja z energijo nič, v njeni okolici pa se nahaja široko območje brez energijske reže. Glavnina dela je posvečena proučevanju počasnih preklopov Hamiltonjana preko omenjene kritične točke. Med preklopom se pojavijo ekscitacije v prevodnem pasu, katerih število skalira kot potenčna funkcija hitrosti preklopa z logaritemskim popravkom. Potenčno odvisnost opazimo tudi pri skaliranju energij najvišje vzbujenih elektronov s hitrostjo preklopa. Pri dovolj počasnih preklopih se pojavi univerzalna časovna odvisnost števila ekscitacij od časa. Delo zaključimo s podrobnejšo analizo posameznih ekscitacij in ugotovimo, da preklopljeno stanje praviloma preide v le dve stanji v prevodnem pasu.

Keywords

topološki izolatorji;model Su-Schrieffer-Heeger;nered;Andersonova lokalizacija;preklopi;

Data

Language:	Slovenian
Year of publishing:	2020
Typology:	2.09 - Master's Thesis
Organization:	UL FMF - Faculty of Mathematics and Physics
Publisher:	[A. Kolar-Požun]
UDC:	538.9
COBISS:	34893315
Views:	400
Downloads:	97
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Quenches Between Topological Phases in a Disordered Su-Schrieffer-Heeger Model
Secondary abstract:	We consider a disordered Su-Schrieffer-Heeger model. In such a system a transition between topological phases is also possible by changing the strength of the disorder. The critical point of this phase transition coincides with the delocalization of the zero energy state, while in its neighbourhood we observe a wide area without the energy gap. The main part of our work is devoted to the study of slow Hamiltonian quenches over the previously mentioned critical point. During the quench, excitations in the conduction band appear with their number scaling as a power law of the quench speed with a logarithmic correction. A power law scaling is also observed in the dependence of the highest excited electrons' energies on the quench speed. For slow enough quenches we find universal dependence of the number of excitations on time. We conclude with a detailed analysis of individual excitations and notice that the quenched state generally transitions to only two states in the conduction band.
Secondary keywords:	topological insulators;Su-Schrieffer-Heeger model;disorder;Anderson localization;quenches;
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:	60 str.
ID:	12098895