Page 12 - Electrical Properties of Materials

Contents xi

13.11 Electro-absorption in quantum well structures 364
13.11.1 Excitons 364
13.11.2 Excitons in quantum wells 365
13.11.3 Electro-absorption 365
13.11.4 Applications 367
Exercises 369

14 Superconductivity

14.1 Introduction 371
14.2 The effect of a magnetic field 373
14.2.1 The critical magnetic field 373
14.2.2 The Meissner effect 374
14.3 Microscopic theory 375
14.4 Thermodynamical treatment 376
14.5 Surface energy 381
14.6 The Landau–Ginzburg theory 382
14.7 The energy gap 389
14.8 Some applications 393
14.8.1 High-field magnets 393
14.8.2 Switches and memory elements 394
14.8.3 Magnetometers 394
14.8.4 Metrology 395
14.8.5 Suspension systems and motors 395
14.8.6 Radiation detectors 395
14.8.7 Heat valves 396
14.9 High-T c superconductors 396
14.10 New superconductors 401
Exercises 403

15 Artificial materials or metamaterials

15.1 Introduction 404
15.2 Natural and artificial materials 405
15.3 Photonic bandgap materials 407
15.4 Equivalent plasma frequency of a wire medium 408
15.5 Resonant elements for metamaterials 410
15.6 Polarizability of a current-carrying resonant loop 411
15.7 Effective permeability 412
15.8 Effect of negative material constants 414
15.9 The ‘perfect’ lens 417
15.10 Detectors for magnetic resonance imaging 422

Epilogue 424

Appendix I: Organic semiconductors 427
Appendix II: Nobel laureates 434
Appendix III: Physical constants 436
Appendix IV: Variational calculus. Derivation of Euler’s equation 438
Appendix V: Thermoelectricity 440