Measuring, Interpreting and Translating Electron Quasiparticle - Phonon Interactions on the Surfaces of the Topological Insulators Bismuth Selenide and Bismuth Telluride (eBook)

Colin Howard (Autor)

eBook Download: PDF

2016 | 1st ed. 2016
XV, 88 Seiten
Springer International Publishing (Verlag)
978-3-319-44723-0 (ISBN)

Infos

The thesis presents experimental and theoretical results about the surface dynamics and the surface Dirac fermion (DF) spectral function of the strong topological insulators Bi2Te3 and Bi2Se3. The experimental results reveal the presence of a strong Kohn anomaly in the measured surface phonon dispersion of a low-lying optical mode, and the absence of surface Rayleigh acoustic phonons. Fitting the experimental data to theoretical models employing phonon Matsubara functions allowed the extraction of the matrix elements of the coupling Hamiltonian and the modifications to the surface phonon propagator that are encoded in the phonon self-energy. This allowed, for the first time, calculation of phonon mode-specific DF coupling λ_ν(q) from experimental data, with average coupling significantly higher than typical values for metals, underscoring the strong coupling between optical surface phonons and surface DFs in topological insulators. Finally, to connect to experimental results obtained from photoemission spectroscopies, an electronic (DF) Matsubara function was constructed using the determined electron-phonon matrix elements and the optical phonon dispersion. This allowed calculation of the DF spectral function and density of states, allowing for comparison with photoemission and scanning tunneling spectroscopies. The results set the necessary energy resolution and extraction methodology for calculating λ from the DF perspective.

Dr Colin Howard was awarded a PhD from Boston University in 2015.  In 2012 he received the Gertrude and Maurice Goldhaber Award for Excellence in Physics Research, awarded annually to a single graduate student at Boston University for making exceptional contributions to research in their first year of graduate study.

Inhalt

Supervisor's Foreword 7
Abstract 9
Acknowledgments 11
Contents 13
List of Abbreviations 15
1 Introduction 16
References 20
2 Properties of Bi2Se3 and Bi2Te3 22
2.1 Crystal Structure 22
2.2 Bulk Vibrational Structure 24
2.3 Electronic Structure 26
References 29
3 Helium Atom-Surface Scattering (HASS) 30
3.1 The Benefits of HASS 30
3.2 The Surface Interaction Potential 31
3.3 The Kinematics of HASS 33
3.3.1 Elastic Scattering 33
3.3.2 Inelastic Scattering and Time-of-Flight Technique 34
References 37
4 Experimental Apparatus and Technique 38
4.1 Surface Laboratory Facilities 38
4.2 Source Chamber 38
4.3 Target Chamber 41
4.3.1 Production and Monitoring of UHV 42
4.3.2 Sample Manipulator 42
4.3.3 Sample Cleaver 43
4.3.4 Helium Detector 44
4.3.4.1 Continuous (Elastic) Detection 44
4.3.4.2 Time-of-Flight (Inelastic) Detection 44
References 46
5 Pseudocharge Phonon Model 47
5.1 Fundamentals of the Model 47
5.2 Adiatbatic Approximation, Ionic Self-Terms, and PC Self-Terms 48
5.3 Bulk Parameters 50
5.4 Surface Parameters 55
References 56
6 HASS Results from the Surface of Bi2Se3 and Bi2Te3 57
6.1 Elastic and Inelastic Scattering Results 57
6.2 Calculation of EPC Parameter in the RandomPhase Approximation 62
References 67
7 Translating Between Electron and Phonon Perspectives 68
7.1 Motivation 68
7.2 DFQ Self-Energy Formalism 69
7.3 Computational Results 71
7.4 Additional Supporting Results 75
References 77
8 Conclusion and Future Directions 78
8.1 Summary 78
8.2 Future Work 79
References 83
A Supplemental Material for Electron Self-Energy Analysis 84
A.1 Electron Green's Function 84
A.2 Bosonic Sums 90
B Numerical Evaluation of the DFQ Self-Energy 93
B.1 Hole Term 94
B.1.1 Above Dirac Point 94
B.1.2 Below Dirac Point 98
B.2 Particle Term 98
B.2.1 Above Dirac Point 98
B.2.2 Below Dirac Point 99
B.3 Interband Transitions 100

Produkt-Details

• Erscheint lt. Verlag: 14.10.2016
• Reihe/Serie: Springer Theses
• Reihe/Serie: Springer Theses
• Zusatzinfo: XV, 88 p. 41 illus., 33 illus. in color.
• Verlagsort: Cham
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Atom- / Kern- / Molekularphysik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Theoretische Physik
• Themenwelt: Technik ► Maschinenbau
• Schlagworte: Bismuth selenide and bismuth telluride • Dirac fermion quasiparticles (DFQs) • HASS spectroscopy • Inelastic helium atom surface scattering spectroscopy • optical surface phonons • quasiparticle phonon coupling • strong topological insulators • surface phonon dispersion
• ISBN-10: 3-319-44723-8 / 3319447238
• ISBN-13: 978-3-319-44723-0 / 9783319447230