Table of Contents
Preface v
List of Acronyms xv
Introduction 1
0.1 Origin of Spintronics - GMR Effect Device 2
0.2 New Materials for Spintronics Applications 3
0.3 Spin Injection and Spin Transport of Electrons 5
0.4 Optical Modulation of Spin Coherence in Semiconductors and Nanostructures 7
0.5 Spin Electronic Devices 10
References 12
1 Properties of Magnetic Ions in Semiconductors 14
1.1 Electron Configuration of Magnetic Ions 14
1.2 Splitting of the Basis State of Free Ions in the Crystal Field 17
1.3 Crystal Field Theory 19
1.4 Wave Functions of Many-electron States 22
1.5 Equivalent Operator Method 25
1.6 Magnetic Ion Energy Levels in Semiconductors 27
1.7 Experimental Study of the Properties of Magnetic Ions in Semiconductors 33
References 38
2 Properties of DMSs 40
2.1 Effective-mass Theory of Semiconductors in the Magnetic Field 42
2.2 DMSs of a Wide Band Gap 43
2.2.1 Magnetic energy levels of wide bandgap semiconductors 43
2.2.2 Magnetic interaction in DMSs 50
2.2.3 DMSs of the wurtzite structure 55
2.2.4 Experimental observations 57
2.3 Narrow Bandgap DMSs 66
2.3.1 Magnetic energy levels of narrow bandgap semiconductors 66
2.3.2 Magnetic optical spectra of Hg1-xMnxTe 70
2.4 Microstructures of DMSs 73
2.4.1 DMS superlattices (Faraday configuration) 73
2.4.2 DMS superlattice (Voigt configuration) 78
2.4.3 DMS quantum dots 84
2.4.4 MP effect 91
2.4.5 DMS quantum wires 97
2.5 Transport Properties of DMSs 101
2.6 Fe2+ Ion-doped DMSs - Van Vleck Paramagnetism 105
2.7 Giant Faraday Rotation and KR 107
2.7.1 Magneto-optical property of magnetic semiconductors 107
2.7.2 TRFR and TRKR in magnetic semiconductors 112
2.8 Light-Induced Magnetization 114
References 119
3 Ferromagnetic Semiconductors 122
3.1 FMS Ga1-xMnxAs 123
3.2 Other FMSs 131
3.3 Fermi-level Engineering 139
3.4 Influence of Clusters on Ferromagnetism 143
3.5 QDs of FMSs 146
3.6 Mean-field Theory of FMSs 150
3.6.1 Microscopic theory of ferromagnetism 150
3.6.2 Magnetic interaction in DMSs 155
3.6.3 FMS quantum wires and quantum slabs 163
3.6.4 Ferromagnetic semiconductor QDs 169
3.7 First-principle Calculation of FMSs 172
3.7.1 Simple model of the electronic structure of 3d impurities in GaAs 173
3.7.2 Practical rules for ferromagnetism of 3d impurities in semiconductors 176
3.8 Magnetic Polaron (MP) - A New Mechanism of Ferromagnetism 180
References 185
4 Injection of Spin-polarized Electrons 187
4.1 Spin Lifetime and Drift of Electrons in Semiconductors 187
4.2 Rashba Effect 198
4.2.1 Origin of the Rashba effect 198
4.2.2 Experimental measurement of the Rashba coefficient 201
4.2.3 Theoretical calculation of the Rashba coefficient 206
4.3 Semiconductor Spin Transistor and Quantum Waveguide Theory 210
4.3.1 Spin-polarized tunneling transistor 210
4.3.2 Semiconductor spin transistor 213
4.4 Quantum Waveguide Theory of Rashba Electrons 217
4.4.1 1D quantum waveguide theory of Rashba electrons 218
4.4.2 Transport in closed ID loops 223
4.4.3 Eigenstates in closed loops 225
4.5 Production and Transport of Spin-polarized Current 227
4.5.1 Coherent transport of spin-polarized electrons through an interface of heterostructure 227
4.5.2 Injection of spin-polarized electrons (experiment) 234
4.5.3 Injection of spin-polarized electrons (theory) 241
4.6 Magnetic Semiconductor Tunneling Junction 251
4.6.1 Property of GaAs/GaMnAs heterostructures 251
4.6.2 FM/NM/FM trilayer 252
4.6.3 Hybridized structure of ferromagnetic metals and semiconductors 257
References 262
5 Spin Relaxation 264
5.1 SRTs T1 and T2 264
5.2 Elliot-Yafet Relaxation Mechanism 265
5.3 Dyakonov-Perel Relaxation Mechanism 272
5.4 Bir-Aronov-Pikus Mechanism 277
5.5 Experimental Studies of Spin Relaxation in III-V Compounds 279
5.5.1 Optical orientation method 279
5.5.2 Spin relaxation in InSb (EY mechanism) 283
5.5.3 Spin relaxation in GaAs (DP mechanism) 284
5.5.4 Spin relaxation in GaAs (BAP mechanism) 285
5.5.5 Dependence of spin relaxation rate on acceptor concentration 289
5.6 Spin Relaxation in Quantum Wells 290
5.7 Electron Spin Relaxation Studied by a Kinetic Spin Bloch Equation 298
5.7.1 Kinetic spin Bloch equation 298
5.7.2 Comparison of different spin relaxation mechanisms 299
5.7.3 DP spin relaxation in n-type GaAs 300
5.7.4 Spin relaxation in intrinsic GaAs 302
5.7.5 Electron spin relaxation in p-type GaAs 304
References 306
6 Rashba and Dresselhaus Effects 307
6.1 Spin Splitting Induced by Spin-Orbit Interaction (SOI) in Inversion Asymmetrical Semiconductors ? Rashba and Dresselhaus Effects 307
6.1.1 Effective mass approximation 307
6.1.2 General description of the Dresselhaus effect 315
6.1.3 Relativistic quantum mechanical understanding 318
6.2 The SOI Hamiltonian in a Rashba System 326
6.3 The Rashba Effect and Dispersion 328
6.4 Rashba Parameter α 330
6.4.1 The k p equation 331
6.4.2 The k p treatment of SOI 333
6.4.3 The eight bands model 333
6.4.4 The five bands model 336
6.5 Deriving the Rashba Coefficient α from the SdH Oscillation 339
6.6 Spin-related Scattering and Spin Current 343
6.6.1 Scattering related to spin 345
6.6.2 Spin current and magnetocurrent 346
References 353
7 Optical Responses of Electron Spins in Semiconductors 354
7.1 Spin of Photon or Polarization of Light 355
7.2 Spin Conservation in Optical Transitions in Semiconductors 356
7.2.1 Selection rules of optical transitions 356
7.2.2 Optical excitation for spin-split bands 358
7.3 Spin Photocurrent Induced by Optically Injected Electron Spin in a Spin Splitting System 363
7.3.1 Circular photogalvanic effect 363
7.3.2 Anomalous CPGE 369
7.3.3 Spin galvanic effect (SGE) 372
7.3.4 Linear photogalvanic effect 373
7.4 Electric Field-induced Electron Spin Polarization in a Spin-Split System 375
7.5 The Experimental Distinction and Applications of the Rashba and Dresselhaus Effects 378
7.6 Spin Electronic and Opto-electronic Devices 383
7.6.1 Spin FET based on combined Rashba and Dresselhaus effects 383
7.6.2 Spin light resources - LED and laser 387
7.6.3 Detecting spin current by electric current 398
References 404
8 Manipulation of Spin Coherent Electrons 406
8.1 Experimental Methods 406
8.2 Electron Spin Coherence in Semiconductor Bulk Materials 411
8.3 Electron Spin Coherence in Semiconductor QDs 413
8.4 Spatial Movement of Spin Coherent Electrons in Semiconductors 419
8.4.1 Spatial movement of coherent spin in compound semiconductors 419
8.4.2 Current-induced spin polarization 422
8.5 Spin Hall Effect 425
8.5.1 Optical observation of the spin Hall effect 425
8.5.2 Spin Hall effect in 2DEGs 432
8.6 Generation of Spin Current 434
8.6.1 Spin current generated by the spin Hall effect 435
8.6.2 Spin current generated by a two-color light field 437
8.7 Spin Dynamics in Semiconductors 443
8.7.1 Mobility and diffusion coefficient of spin current 444
8.7.2 Effect of electric field on spin-polarized current 448
8.8 Coherent Manipulation of a Single Spin in Semiconductors 451
8.8.1 Single-spin rotations 452
8.8.2 Quantum control of a single QD spin using ultrafast optical pulses 454
8.9 Spin Polarization and Transport in Silicon 458
8.9.1 Measurement and control of spin transport in silicon 458
8.9.2 Electrical injection of spin polarization in silicon at RT 462
References 465
9 Spin-Polarized Electron and Domain Wall Transport 467
9.1 Spin Transport in Magnetic Semiconductor 2DEG 467
9.2 Spin Transport Through QDs 476
9.2.1 Spin transport through the double barrier tunneling junctions with ferromagnetic leads 476
9.2.2 The Kondo effect in semiconductor QDs with ferromagnetic leads 480
9.2.3 Theory of spin transport through magnetic semiconductor QDs 485
9.3 Magnetic Domain Transport in Magnetic Semiconductors 488
References 494
10 Future Quantum Dot and Quantum Wire Spintronics 497
10.1 Electron Structure and g-Factor of QDs 499
10.2 Electron Structure and g-Factor of Quantum Wires 510
10.3 Electric Field Tunable g-Factor in QDs 515
10.4 Influence of N Doping on the Rashba Coefficient and the g-Factor of Electrons 518
References 521
Index 523
