1 Onnes' discovery and one hundred years of superconductors .... 1
1.1 Onnes' discovery ........................................ 2
1.2 One hundred years of superconductors .................... 3
1.3 Progress with LTS and HTS applications ................. 11
1.4 This book .............................................. 13
1.5 Summary ................................................ 13
2 The superconducting state ................................... 15
2.1 Electrical conduction in metals and the origin of
resistance ............................................. 15
2.2 Microscopic nature of superconducting state ............ 18
2.3 Summary ................................................ 27
Appendix 2A: BCS ground state and the energy gap ............ 27
3 The superconducting transition and its basic
phenomenology ............................................... 31
3.1 Fundamental characteristics of the superconducting
transition ............................................. 31
3.2 The critical field Hc .................................. 32
3.3 The critical current ................................... 33
3.4 Resistive transition ................................... 33
3.5 Implications of perfect conductivity ................... 35
3.6 Meissner-Ochsenfeld effect ............................. 36
3.7 London phenomenology ................................... 37
3.8 Penetration depth ...................................... 38
3.9 Depairing current density .............................. 39
3.10 Shortcomings of the London phenomenology ............... 39
3.11 Intermediate state ..................................... 40
3.12 Filamentary superconductors and Mendelssohn's sponge ... 40
3.13 Range of coherence and non-local theory ................ 41
3.14 Interface boundary energy .............................. 43
3.15 Summary ................................................ 43
Appendix 3А: Electrodynamics of a perfect conductor and
London phenomenology ........................................ 43
4 Thermodynamics and general properties ....................... 47
4.1 Thermodynamic aspects of the transition ................ 47
4.2 Thermal properties ..................................... 48
4.3 Ultrasonic behaviour ................................... 53
4.4 AC and optical properties .............................. 54
4.5 Tunnelling in the superconducting state ................ 55
4.6 Summary ................................................ 60
Appendix 4A ................................................. 61
4A.1 Condensation energy .................................... 61
4A.2 Entropy ................................................ 62
4A.3 Heat capacity .......................................... 62
5 Advent of type II superconductors ........................... 65
5.1 Ginzburg-Landau phenomenology .......................... 65
5.2 Sign of the surface energy and superconductor types .... 69
5.3 Mixed state and other characteristics .................. 71
5.4 Summary ................................................ 75
Appendix 5A: Ginzburg-Landau equations ...................... 76
6 Critical current and flux pinning ........................... 79
6.1 Transport current in the mixed state ................... 79
6.2 Driving force and the critical state ................... 81
6.3 Vortex motion .......................................... 83
6.4 Stabilisation of superconductors ....................... 87
6.5 Pinning centres ........................................ 89
6.6 Pinning interactions ................................... 92
6.7 AC losses .............................................. 94
6.8 Summary ................................................ 95
7 Superconductors in abundance ................................ 97
7.1 Low-temperature superconductors (LTS) .................. 98
7.2 High-temperature superconductors (HTS) ................ 109
7.3 Summary ............................................... 114
8 Niobium-zirconium and niobium-titanium alloys .............. 115
8.1 The niobium-zirconium system .......................... 116
8.2 The niobium-titanium system ........................... 119
8.3 Summary ............................................... 125
9 A-15 superconductors ....................................... 127
9.1 Crystal structure, stoichiometry and ordering ......... 128
9.2 Long-range order and Tc ............................... 131
9.3 Structural instability at low temperature ............. 132
9.4 Potential binary systems .............................. 133
9.5 Pseudo-binaries ....................................... 134
9.6 A-15 phase formation .................................. 135
9.7 Upper critical field and paramagnetic limitation ...... 136
9.8 Critical current density and the nature of pinning
centres in A-15s ...................................... 137
9.9 Strain sensitivity .................................... 139
9.10 Summary ............................................... 140
10 Conductor development of A-15 superconductors .............. 141
10.1 Liquid-solute diffusion ............................... 141
10.2 CVD process ........................................... 142
10.3 The bronze process and formation of A-15 phase by
solid state diffusion ................................. 143
10.4 Thermodynamics and kinetics of compound-layer
formation in the bronze process ....................... 147
10.5 Modifications of the bronze process ................... 154
10.6 Fabrication of Nb3Al conductor ........................ 157
10.7 Summary ............................................... 161
11 Chevrel-phase superconductors .............................. 163
11.1 Crystal structure and stoichiometry ................... 165
11.2 Occurrence of superconductivity in Chevrel phases ..... 166
11.3 Synthesis of bulk samples ............................. 170
11.4 Upper critical field .................................. 171
11.5 Critical current density: inherent problems and
progress in raising Jc ................................ 171
11.6 Conductor development of Chevrel-phase compounds ...... 175
11.7 Nature of superconductivity of Chevrel-phase
compounds ............................................. 176
11.8 Summary ............................................... 178
12 Rare-earth-based ternary superconductors and quaternary
borocarbides ............................................... 181
12.1 LTS systems with magnetic order ....................... 182
12.2 The interplay ......................................... 183
12.3 Various ternary materials and their interplay
behaviour ............................................. 183
12.4 Quaternary borocarbides ............................... 189
12.5 Crystal structure and related aspects ................. 190
12.6 Coexistence and interplay of Tc and Tm ................ 191
12.7 Summary ............................................... 198
13 Heavy fermion superconductors .............................. 201
13.1 Discovery of HF superconductors ....................... 201
13.2 Quantum phase transition and quantum critical point ... 202
13.3 General features of anomalous normal state and
unusual superconductivity ............................. 204
13.4 Short description of various HF superconductors ....... 207
13.5 Special features of HF superconductors ................ 220
13.6 Summary ............................................... 226
14 Organic superconductors .................................... 227
14.1 Evolution of organic superconducting salts ............ 227
14.2 The (TM)2 family of quasi-one-dimensional
superconductors ....................................... 231
14.3 The (ET)2 family of quasi-two-dimensional
superconductors ....................................... 236
14.4 Superconducting fullerides ............................ 245
14.5 Graphite intercalation compounds (GICs) ............... 251
14.6 Summary ............................................... 253
15 Superconducting magnesium diboride ......................... 255
15.1 Crystal structure and Tc .............................. 256
15.2 Conventional superconductivity of MgB2 ................ 259
15.3 Band structure and two superconducting gaps ........... 261
15.4 Implications of two gaps .............................. 262
15.5 MgB2 for practical applications ....................... 263
15.6 Material synthesis .................................... 265
15.7 Nanoparticle doping for enhancing Jc .................. 266
15.4 Conductor development: wires and tapes of MgB2 ........ 269
15.9 Summary ............................................... 271
16 High-temperature cuprate superconductors ................... 273
16.1 Genesis of HTS cuprates ............................... 274
16.2 General features of HTS cuprates ...................... 277
16.3 Prominent HTS cuprate systems ......................... 289
16.4 Substitution studies in HTS ........................... 293
16.5 Summary ............................................... 295
17 Thin-film technology and conductor development of HTS
cuprates ................................................... 297
17.1 Microstructural aspects ............................... 297
17.2 Prominent techniques for depositing HTS films ......... 301
17.3 Conductor development ................................. 310
17.4 Summary ............................................... 323
18 Bulk HTS cuprates .......................................... 325
18.1 General considerations ................................ 326
18.2 Melt processing ofbulkYBCO samples .................... 326
18.3 Effective pinning centres in bulk HTS ................. 332
18.4 Ternary 123 bulk compounds ............................ 334
18.5 Trapped field ......................................... 335
18.6 Mechanical strengthening .............................. 336
18.7 Summary ............................................... 338
19 Ruthenates and ruthenocuprates ............................. 339
19.1 A superconductor in the ruthenate family: Sr2Ru04 ..... 339
19.2 Unconventional superconductivity ...................... 344
19.3 Summary of the current status of ruthenate
superconductors ....................................... 346
19.4 Superconducting ruthenocuprates ....................... 347
19.5 Superconductivity, general features ................... 352
19.6 Magnetic states and coexistence of Тм and Tc .......... 358
19.7 Cationic substitutions in Ru-1212 and Ru-1222,
effect on Tc and TM ................................... 363
19.8 Summary ............................................... 365
20 Iron-based superconductors ................................. 367
20.1 Different FBS families, their crystal structures,
and their general features ............................ 367
20.2 Electronic structure .................................. 376
20.3 Phase diagrams ........................................ 377
20.4 Unconventional superconductivity of FBS ............... 379
20.5 Materials synthesis ................................... 383
20.6 Upper critical field, anisotropy, and potential for
applications .......................................... 384
20.7 Summary ............................................... 389
21 Miscellaneous superconductors .............................. 391
21.1 Superconducting bismuthates ........................... 391
21.2 Cobalt oxide hydrate .................................. 398
21.3 Intermetallic perovskites free from oxygen: MgCNi3
and related superconducting compounds ................. 406
21.4 Metallonitride halides ................................ 410
21.5 Pyrochlore oxides ..................................... 414
21.6 Layered transition metal chalcogenides ................ 420
21.7 BiS2-based superconductors ............................ 426
References .................................................... 431
Index ......................................................... 471
|
