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EMERGENT PHENOMENA FROM SPIN DEGREES OF FREEDOM IN LOW-DIMENSIONAL SYSTEMS : 낮은 차원계의 스핀 자유도를 통한 떠오름 현상
DC Field | Value | Language |
---|---|---|
dc.contributor.advisor | 최무영 | - |
dc.contributor.author | 이형준 | - |
dc.date.accessioned | 2017-07-19T06:13:36Z | - |
dc.date.available | 2017-07-19T06:13:36Z | - |
dc.date.issued | 2017-02 | - |
dc.identifier.other | 000000142613 | - |
dc.identifier.uri | http://dcollection.snu.ac.kr:80/jsp/common/DcLoOrgPer.jsp?sItemId=000000142613 | - |
dc.description | 학위논문(박사)--서울대학교 대학원 :자연과학대학 물리·천문학부,2017. 2. 최무영. | - |
dc.description.abstract | We study emergent phenomena that occur in low dimensional spin and electronic systems, especially those related to spin degrees of freedom. In frustrated ferromagnetic spin-1 chains where the ferromagnetic nearest-neighbor coupling competes with the antiferromagnetic next-nearest-neighbor coupling, we analyze the ground state and its various correlation functions by using the density-matrix renormalization group. The double Haldane phase with ferromagnetic coupling shows incommensurate correlations of wavenumber $q$ with $0Such short-range correlations transform continuously
into the ferromagnetic instability at the transition. The additional anisotropy in exchange interaction gives rise to a new disordered phase and a chirality phase in a wide region. We also compare the results with the spin-1/2 and classical spin systems, and discuss the string orders in the system. We also investigate the magnetism on the edge of the Kane-Mele-Hubbard model. By means of the Hartree-Fock approximation we examine the nature of edge states in the presence of the Hubbard interaction in the Kane-Mele model. We compute local magnetizations of a nanoribbon with various widths. Phase diagram is obtained in the thermodynamic limit. It turns out that in-plane magnetic order survives at the edges in a wide range of the spin-orbit coupling. The variation of its characteristic length is shown to be closely related to the phase transition between topological insulator and antiferromagnetic insulator. | - |
dc.description.tableofcontents | 1 Introduction 1
2 Reviews of quantum spin chains 6 2.1 Spin-1 chain models 7 2.1.1 AKLT (A eck-Kennedy-Lieb-Tasaki) state 8 2.1.2 Heisenberg spin chains 10 2.1.3 String correlation 13 2.1.4 Matrix-product states 15 2.1.5 Frustrated spin chains 24 2.1.6 Anisotropy e ects 29 2.2 Experiments on spin-1 chain systems 36 3 Methods 41 3.1 Density-matrix renormalization-group (DMRG) 41 3.1.1 Ground state and Truncation 42 3.1.2 Exact diagonalization 48 3.1.3 Physical quantities 52 3.1.4 Excited states 53 3.1.5 Physical considerations 54 3.1.6 Optimizations 60 3.2 Hartree-Fock approximation 64 4 Frustrated Spin-1 Chains 69 4.1 Model 69 4.2 Results 70 4.3 Summary 84 5 Anisotropy in spin chains 86 5.1 Model 87 5.2 Results 87 5.3 Summary 99 6 Kane-Mele-Hubbard model 101 6.1 Introduction 101 6.2 Model 105 6.3 Results 108 6.4 Summary 116 Bibliography 117 Abstract in Korean 128 | - |
dc.format.extent | xiv, 129 | - |
dc.language.iso | eng | - |
dc.publisher | 서울대학교 대학원 | - |
dc.subject | quantum spin chain, Haldane gap, AKLT state, frustration, anisotropy, density-matrix renormalization-group, Kane-Mele-Hubbard model, Hartree-Fock approximation | - |
dc.subject.ddc | 523 | - |
dc.title | EMERGENT PHENOMENA FROM SPIN DEGREES OF FREEDOM IN LOW-DIMENSIONAL SYSTEMS | - |
dc.title.alternative | 낮은 차원계의 스핀 자유도를 통한 떠오름 현상 | - |
dc.type | Thesis | - |
dc.type | Dissertation | - |
dc.contributor.AlternativeAuthor | Hyeong Jun Lee | - |
dc.contributor.department | 자연과학대학 물리·천문학부 | - |
dc.description.degree | Doctor | - |
dc.date.awarded | 2017-02 | - |
dc.identifier.holdings | 000000000030▲000000000031▲000000142613▲ | - |
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