Abstract ........................................................ i
1 Introduction ................................................. 1
2 Basics of electrodynamics of solids .......................... 3
2.1 Optical properties of solids ............................ 3
2.1.1 Drude-Sommerfeld model ........................... 3
2.1.2 Lorentz model .................................... 8
2.1.3 Extended Drude analysis .......................... 9
2.2 Superconductivity ...................................... 10
2.2.1 London theory of superconductivity .............. 10
2.2.2 BCS theory of superconductivity ................. 12
2.2.3 Electrodynamics of the superconducting state .... 15
2.2.4 Eliashberg theory ............................... 22
2.3 Superconductivity in strongly correlated electron
systems ................................................ 23
2.3.1 High-temperature cuprate superconductors ........ 23
2.3.2 Superconductivity in iron-based
superconductors ................................. 26
3 Experimental methods: Optical spectroscopy .................. 31
3.1 Terahertz spectroscopy ................................. 32
3.1.1 Backward-wave-oscillator-based spectroscopy ..... 32
3.1.2 Time-domain terahertz spectroscopy .............. 35
3.2 Infrared spectroscopy .................................. 37
3.3 NIR-visible-ultraviolet spectroscopy ................... 41
4 Data analysis ............................................... 43
4.1 Analysis of phase-sensitive transmission data .......... 43
4.1.1 Analysis of phase-sensitive ВWO data ............ 43
4.1.2 Analysis of time-domain terahertz-spectroscopy
data ............................................ 44
4.2 Analysis of reflectivity data .......................... 46
4.2.1 Merging of reflectivity data .................... 46
4.2.2 Data extrapolation .............................. 47
4.2.3 Kramers-Kronig analysis ......................... 48
4.2.4 Fitting of reflectivity and conductivity data ... 49
4.2.5 Spectral-weight analysis ........................ 50
4.2.6 Extended Drude analysis ......................... 51
5 Niobium thin film ........................................... 53
5.1 Introduction ........................................... 53
5.2 Experimental details ................................... 54
5.3 Resistivity ............................................ 54
5.4 Transmission ........................................... 55
5.5 Complex conductivity ................................... 59
5.6 Extended Drude analysis ................................ 63
5.7 Penetration depth ...................................... 65
5.8 Summary ................................................ 68
6 Nominally undoped Pr2CuO4 thin film ......................... 69
6.1 Introduction ........................................... 69
6.2 Experimental details ................................... 71
6.3 Resistivity ............................................ 73
6.4 Reflectivity ........................................... 76
6.5 Complex conductivity ................................... 78
6.6 Extended-Drude and Eliashberg analysis ................. 84
6.7 Penetration depth ...................................... 90
6.8 Pseudogap feature ...................................... 94
6.9 Summary ................................................ 95
7 FeTe0.5Se0.5 thin film ....................................... 97
7.1 Introduction ........................................... 97
7.2 Samples and experimental details ....................... 98
7.3 Resistivity ............................................ 99
7.4 Transmission .......................................... 100
f:5 Complex conductivity ................................. 103
7.6 Extended Drude analysis ............................... 107
7.7 Penetration depth ..................................... 108
7.8 Summary ............................................... 114
8 LiFeAs single crystal ...................................... 115
8.1 Introduction .......................................... 115
8.2 Experimental details .................................. 115
8.3 Reflectivity .......................................... 116
8.4 Complex conductivity, penetration depth, and clean-
limit superconductivity ............................... 117
8.5 Decomposition of the real part of optical
conductivity .......................................... 122
8.6 Extended Drude analysis ............................... 124
8.7 Summary ............................................... 126
9 Conclusion ................................................. 127
Appendix ...................................................... 131
Appendix A: DyScO3 ......................................... 131
Appendix B: Thin Films Optical Conductivity ................ 133
Bibliography .................................................. 137
Acknowledgment ................................................ 155
Versicherung .................................................. 157
|
