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Table of Contents
Intro
Supervisor's Foreword
Abstract
Acknowledgments
Contents
Abbreviations
1 Introduction
1.1 Experimental Signatures of Topological Metals
1.1.1 ARPES and the Discovery of Weyl Semimetals
1.1.2 The Chiral Anomaly and Negative Magnetoresistance of Weyl Semimetals
1.1.3 Optical Responses as Probes for Topological Phases
1.2 Beyond Weyl Crossings: Multifold Fermions
1.3 Structure of the Thesis
References
2 Chiral Multifold Fermions
2.1 Weyl Fermions
2.2 The Classification of Chiral Multifold Fermions
2.2.1 Double-Weyl Fermion
2.2.2 Threefold Fermion
2.2.3 Sixfold Fermion
2.2.4 Fourfold Fermion
2.3 Material-Oriented Tight-Binding Models of Chiral Multifold Fermions
2.3.1 Space Group 199
2.3.2 Space Group 198 and Candidate Materials
2.4 Conclusions
References
3 Linear Optical Conductivity of Chiral Multifold Fermions: kcdotp and Tight-Binding Models
3.1 Linear Optical Response in the Length Gauge
3.2 Optical Fingerprints in the Multifold kcdotp Models
3.2.1 Optical Conductivity of Fully Rotationally Symmetric Models
3.2.2 Optical Conductivity of Non-symmetric Low-Energy Models
3.3 Imaginary Part of the Optical Conductivity and Sum Rules
3.4 Optical Conductivity of Realistic Tight-Binding Models
3.4.1 Space Group 199
3.4.2 Space Group 198: RhSi
3.5 Conclusions
References
4 Linear Optical Conductivity of CoSi and RhSi: Experimental Fingerprints of Chiral Multifold Fermions in Real Materials
4.1 Introduction
4.2 CoSi
4.2.1 Experimental Features of the Optical Conductivity
4.2.2 Low-Energy Regime: kcdotp and Tight-Binding Models
4.2.3 The Role of Spin-Orbit Coupling and the Spin-3/2 Multifold Fermion
4.2.4 Summary
4.3 RhSi
4.3.1 Experimental Features of the Optical Conductivity
4.3.2 Low-Energy Regime: kcdotp and Tight-Binding Models
4.3.3 Summary
4.4 Conclusions
References
5 Nonlinear Optical Responses: Second-Harmonic Generation in RhSi
5.1 The Zoo of Nonlinear Responses
5.2 The Circular Photogalvanic Effect in RhSi
5.2.1 Experimental Features of the Circular Photogalvanic Effect
5.2.2 DFT Calculation of Circular Photogalvanic Effect in RhSi
5.2.3 Circular Photogalvanic Effect Calculation with a Tight-Binding Model for RhSi
5.3 Second-Harmonic Generation in RhSi
Supervisor's Foreword
Abstract
Acknowledgments
Contents
Abbreviations
1 Introduction
1.1 Experimental Signatures of Topological Metals
1.1.1 ARPES and the Discovery of Weyl Semimetals
1.1.2 The Chiral Anomaly and Negative Magnetoresistance of Weyl Semimetals
1.1.3 Optical Responses as Probes for Topological Phases
1.2 Beyond Weyl Crossings: Multifold Fermions
1.3 Structure of the Thesis
References
2 Chiral Multifold Fermions
2.1 Weyl Fermions
2.2 The Classification of Chiral Multifold Fermions
2.2.1 Double-Weyl Fermion
2.2.2 Threefold Fermion
2.2.3 Sixfold Fermion
2.2.4 Fourfold Fermion
2.3 Material-Oriented Tight-Binding Models of Chiral Multifold Fermions
2.3.1 Space Group 199
2.3.2 Space Group 198 and Candidate Materials
2.4 Conclusions
References
3 Linear Optical Conductivity of Chiral Multifold Fermions: kcdotp and Tight-Binding Models
3.1 Linear Optical Response in the Length Gauge
3.2 Optical Fingerprints in the Multifold kcdotp Models
3.2.1 Optical Conductivity of Fully Rotationally Symmetric Models
3.2.2 Optical Conductivity of Non-symmetric Low-Energy Models
3.3 Imaginary Part of the Optical Conductivity and Sum Rules
3.4 Optical Conductivity of Realistic Tight-Binding Models
3.4.1 Space Group 199
3.4.2 Space Group 198: RhSi
3.5 Conclusions
References
4 Linear Optical Conductivity of CoSi and RhSi: Experimental Fingerprints of Chiral Multifold Fermions in Real Materials
4.1 Introduction
4.2 CoSi
4.2.1 Experimental Features of the Optical Conductivity
4.2.2 Low-Energy Regime: kcdotp and Tight-Binding Models
4.2.3 The Role of Spin-Orbit Coupling and the Spin-3/2 Multifold Fermion
4.2.4 Summary
4.3 RhSi
4.3.1 Experimental Features of the Optical Conductivity
4.3.2 Low-Energy Regime: kcdotp and Tight-Binding Models
4.3.3 Summary
4.4 Conclusions
References
5 Nonlinear Optical Responses: Second-Harmonic Generation in RhSi
5.1 The Zoo of Nonlinear Responses
5.2 The Circular Photogalvanic Effect in RhSi
5.2.1 Experimental Features of the Circular Photogalvanic Effect
5.2.2 DFT Calculation of Circular Photogalvanic Effect in RhSi
5.2.3 Circular Photogalvanic Effect Calculation with a Tight-Binding Model for RhSi
5.3 Second-Harmonic Generation in RhSi