Transport Studies of the Electrical, Magnetic and Thermoelectric properties of Topological Insulator Thin Films (eBook)

Jinsong Zhang received his B.Sc. in Physic in Tsinghua University, P. R. China in 2008. He obtained his Ph.D. in Physics from Physics Department of Tsinghua University in January 2014. His major research project in Prof. Yayu Wang's group was the transport studies of the electric, magnetic and thermoelectric properties in topological insulator thin films. At present, he is a post-doc fellow in Prof. Yi Cui's group in the Department of Material Science and Engineering, Stanford University. His current projects are focusing on the fabrication and characterization of two-dimensional layer materials.

Supervisor’s Foreword 6
Abstract 8
Acknowledgments 10
Contents 11
Publications 14
1 Introduction 16
1.1 Overview of Topological Insulators 16
1.2 Historical Perspective of Topological Insulators 17
1.3 General Theory of Topological Insulators 19
1.3.1 Topological Band Theory 19
1.3.2 Topological Field Theory 22
1.4 Prototypical 3D Topological Materials 23
1.4.1 Theoretical Models 24
1.4.2 Experimental Results 27
1.5 Organization 33
References 34
2 Experimental Setup and Methods 37
2.1 Helium-4 Refrigerator and Superconducting Magnet 37
2.2 Dilution Refrigerator 40
2.3 Probe Design and Temperature Control 43
2.4 Experimental Details of Transport Measurements 45
2.4.1 Electrical Transport Measurements 45
2.4.2 Thermoelectric Transport Measurements 47
2.5 Sample Growth by Molecular Beam Epitaxy 48
2.6 Angle-Resolved Photoemission Spectroscopy 50
References 51
3 Band Structure Engineering in TIs 52
3.1 Band Structure Engineering in Traditional Semiconductors 52
3.2 Motivation and Experimental Design 54
3.3 Experimental Results 55
3.3.1 Sample Characterization 56
3.3.2 Electronic Structure 56
3.3.3 Analysis of the ARPES Data 58
3.3.4 Transport Properties 59
3.3.5 Effect of the Te Capping Layer 63
3.4 Discussion and Conclusion 64
References 65
4 Topology-Driven Magnetic Quantum Phase Transition 67
4.1 Introduction to Magnetic Topological Insulator 67
4.2 Motivation and Experimental Design 69
4.3 Sample Characterization 70
4.4 Transport Measurements 70
4.4.1 Magnetic Quantum Phase Transition in Bi1.78Cr0.22(SexTe1?x)3 72
4.4.2 Methods for the Detection of /rho_{yx}^{0} and xc 76
4.4.3 The High-Field Hall Effect in Bi1.78Cr0.22Te3 76
4.4.4 Magnetic Anisotropy Measurements in Bi1.78Cr0.22Te3 77
4.4.5 Further Proof of Paramagnetism in Bi1.78Cr0.22Se3 78
4.5 SQUID Magnetization Measurements 79
4.6 ARPES Band Mapping 81
4.6.1 Topological Quantum Phase Transition in Bi1.78Cr0.22(SexTe1?x)3 81
4.6.2 Similar Topological QPT in Bi2?yCrySe3 and Bi2?yCryTe3 81
4.7 Density Functional Theory Calculations 84
4.7.1 Calculation Method 84
4.7.2 Band Structures of Bi2?yCrySe3 and Bi2?yCryTe3 84
4.7.3 The Corroboration of Topological QPT in Bi1.75Cr0.25(SexTe1?x)3 87
4.8 Relationship Between Topological QPT and Magnetic QPT 89
4.9 Effective Four-Band Model Calculations 89
4.9.1 The Spin Susceptibility in z Direction 90
4.9.2 Sign Change of the AHE at QCP 91
4.9.3 Physical Meaning and Estimation of Gz1 and Gz2 94
4.10 The van Vleck Mechanism in TIs 94
4.11 Conclusion 96
References 97
5 Quantum Anomalous Hall Effect 99
5.1 Introduction to QAHE 99
5.2 Sample Preparation and Characterization 102
5.3 Quantized Hall Resistance at Zero Magnetic Field 104
5.4 Vanishing Residual Resistance at High Magnetic Field 106
5.5 Evolution of QAHE with Varied Temperatures 107
5.6 Conclusion 108
References 109
6 Dichotomy Between Electrical and Thermoelectric Properties 111
6.1 Introduction to Thermoelectric Effect in TIs 111
6.2 Experimental Design 113
6.3 Electrical and Thermoelectric Measurements 114
6.4 DFT Calculated Band Structures 116
6.5 Calculated Seebeck Coefficient 117
6.6 Discussion on the Sign Anomaly Between RH and Sxx 118
6.7 Conclusion 119
References 119
7 Concluding Remarks 121
Appendix A: Complete Transport Results of QAHE 123
Appendix B: Simple Picture for the Sign of AHE 125
Reference 128