ISBN: 3540421769
TITLE: Semiconductor Spintronics and Quantum Computation
AUTHOR: Awschalom, Loss, Samarth
TOC:

1 Ferromagnetic I-V Semiconductors and Their Heterostructures
Hideo Ohno 1
1.1 Introduction 1
1.2 Preparation of III-V Based Ferromagnetic Semiconductors 2
1.3 Magnetic Properties 4
1.4 Transport Properties 6
1.4.1 The Hall Effect 6
1.4.2 Temperature and Magnetic Field Dependence of Resistivity 8
1.5 Carrier-Induced Ferromagnetism 12
1.6 Basic Properties of Ferromagnetic III-V Semiconductor Heterostructures 16
1.7 Spin-Dependent Scattering and Tunnel Magnetoresistance in Trilaye Structures 17
1.8 Ferromagnetic Emitter Resonant Tunneling Diodes 19
1.9 Spin-Injection
in Ferromagnetic Semiconductor Heterostructures 21
1.10 Electric-Field Control of Hole-Induced Ferromagnetism 23
1.11 Summary and Outlook 25
References 26
2 Spin Injection and Transport in Micro-and Nanoscale Devices
Hong X.Tang,F.G.Monzon,Friso J.Jedema,Andrei T.Filip, Bart J.van Wees,and Michael L.Roukes 31
2.1 Overview 31
2.2 Background 32
2.2.1 Spin Polarized Tunneling 32
2.2.2 Spin Injection in Clean Bulk Metals 33
2.2.3 Conceptual Picture of Spin Injection 36
2.2.4 Spin Injection in Impure Metal Films 39
2.3 Toward a Semiconducting "Spin Transistor"40
2.3.1 Why a Spin Transistor? 40
2.3.2 Why Semiconductors?.40
2.3.3 Concept 41
2.3.4 Prerequisites for Realizing a Spin Transistor 42
2.3.5 Spin Lifetime in the Conduction Channel 43
2.3.6 Gate Control of the Spin Orbit Interaction (Theory).43
2.3.7 Gate Control of the Spin Orbit Interaction (Experiment)44
2.4 Initial Experiments on Spin Injection in Semiconductor Heterostructures 47
2.4.1 Motivation and Initial Data 47
2.4.2 Local Hall Effect 50
2.4.3 Results from Smaller,Optimized Devices 51
2.5 Spin Injection in Diffusive Systems 55
2.5.1 Basic Model for Spin Transport in Diffusive Systems 56
2.5.2 The F/N Interface 58
2.5.3 Spin Accumulation in Multiterminal Spin Valve Structures 59
2.5.4 Observation of Spin-Injection and Spin-Accumulation in an All-Metal Spin Valve 61
2.5.5 Comparison with the Johnson "Spin Transistor".62
2.5.6 Future Prospects for Spin Accumulation and Spin Transport in All Metal Devices 63
2.5.7 Spin Injection in a Diffusive Semiconductor 63
2.5.8 Conductivity Mismatch63
2.5.9 Possible Solutions to Conductivity Mismatch 66
2.6 Spin Transport in the Ballistic Regime 66
2.6.1 Multiprobe Model for Ballistic Spin Polarized Transport 68
2.6.2 Results of Spin Resolved 4-Probe Model 72
2.6.3 8-Probe Model: Junction,Bulk,and Boundary Scattering 75
2.6.4 The Spin Transistor:A Closer Look 77
2.6.5 Other Theoretical Treatments 78
2.7 Projections and Conclusions 79
2.7.1 Retrospective:The Spin Transistor 79
2.7.2 Recent Advances in Spin Transport Across Interfaces 81
2.7.3 Recent Advances in Spin Injection Via Semimagnetic Semiconductors 85
2.7.4 Recent Advances in Spin Propagation in Semiconductors 85
2.7.5 Detection of Nonequilibrium Spin Polarization 86
References 87
3 Electrical Spin Injection:Spin-Polarized Transport from Magnetic into Non-Magnetic Semiconductors
Georg Schmidt and Laurens W.Molenkamp 93
3.1 Introduction 93
3.2 Electrical Spin Injection 94
3.2.1 Diluted Magnetic Semiconductors 94
3.2.2 The Optical Detection of Spin Injection 95
3.2.3 The Spin Aligner LED 96
3.2.4 Experimental Results 97
3.2.5 Exclusion of Side Effects 99
3.2.6 Hole Injection 100
3.3 A Novel Magnetoresistance Effect 101
3.3.1 Theoretical Prediction 101
3.3.2 Device Layout 102
3.3.3 Results and Interpretation 103
3.4 Outlook 104
References 105
4 Spin Dynamics in Semiconductors
Michael E.Flatt ?e,Jeff M.Byers,and Wayne H.Lau 107
4.1 Introduction 107
4.2 Fundamentals of Semiconductor Spin Coherence 108
4.2.1 Coherent Ensembles of Spins 109
4.2.2 Mobile Electron Decoherence Via the Spin-Orbit Interaction 110
4.2.3 Sources of Inversion Asymmetry 115
4.2.4 Comparison with Ultrafast Probes of Orbital Coherence 121
4.2.5 Concluding Remarks 123
4.3 Precessional Spin Coherence Times in Bulk and Nanostructure Semiconductors 123
4.3.1 Magnitude of the Fluctuating Field 125
4.3.2 Calculation of the Effective Time for Field Reversal 126
4.3.3 Spin Decoherence Times in Bulk III-V Semiconductors 126
4.3.4 Spin Decoherence in III-V (001)Quantum Wells 127
4.4 Spin Transport 131
4.4.1 Drift-Diffusion Equations 132
4.4.2 Low-Field Motion of Spin Packets in Nonmagnetic Semiconductors 133
4.4.3 Diffusion and Mobility of Packets in GaAs 135
4.4.4 Influence of Many-Body Effects on Low-Field Spin Diffusion 137
4.4.5 Motion of Spin Packets in Spin-Polarized Semiconductors 138
4.4.6 High-Field Spin Transport in the Diffusive Regime 139
4.5 Spin Transport in Inhomogeneous Structures 139
4.5.1 Transport Across the Ferromagnet/Semiconductor Boundary 140
4.6 Conclusion 142
References 143
5 Optical Manipulation,Transport and Storage of Spin Coherence in Semiconductors
David D.Awschalom and Nitin Samarth 147
5.1 Introduction 147
5.2 Experimental Techniques for Measuring Spin Coherence in Semiconductors 148
5.3 Electron Spin Coherence in Bulk Semiconductors 153
5.4 Electron Spin Coherence in Semiconductor Quantum Dots 160
5.5 Coherent Spin Transport in Semiconductors 162
5.5.1 Lateral Drag in GaAs 162
5.5.2 Transport Across Heterointerfaces in ZnSe/GaAs 166
5.6 Spin Coherence and Magnetic Resonance 175
5.6.1 Electron Paramagnetic Resonance in II-VI Magnetic Semiconductor Quantum Structures 175
5.6.2 All-Optical Nuclear Magnetic Resonance in Semiconductors 177
5.7 Coherent Manipulation of Spin in Semiconductors 181
5.8 Spin Coherence in Hybrid Ferromagnet/Semiconductor Heterostructures 183
5.8.1 Ferromagnetic Imprinting of Nuclear Spins in Semiconductors 184
5.8.2 Spontaneous Electron Spin Coherence in n-GaAs Produced by Ferromagnetic Proximity Polarization 188
5.9 Summary and Outlook 190
References 192
6 Spin Condensates in Semiconductor Microcavities
Jeremy J.Baumberg 195
6.1 Introduction 195
6.2 Polariton Properties 196
6.2.1 Strongly Coupled Microcavity Dispersion 196
6.2.2 Polariton Dynamics and Pair Scattering 200
6.3 Experiments 202
6.3.1 Experimental Geometry 202
6.3.2 Microcavity Sample 203
6.3.3 Parametric Scattering 205
6.4 Condensate Dynamics 211
6.4.1 Polariton Interferometry 211
6.4.2 Macroscopic Quantum States 214
6.4.3 Quantum-Correlated Pairs 216
6.4.4 Conclusions 217
References 218
7 Spins for Quantum Information Processing
David P.DiVincenzo 221
7.1 Introduction 221
7.1.1 The Requirements 222
7.2 Timeline 224
7.3 Final Thoughts 226
References 227
8 Electron Spins in Quantum Dots as Qubits
for Quantum Information Processing
Guido Burkard and Daniel Loss 229
8.1 Introduction 229
8.1.1 Quantum Computing 230
8.1.2 Quantum Communication 231
8.1.3 Quantum Dots 231
8.2 Requirements for Quantum Computing 232
8.2.1 Coherence 232
8.2.2 Slow Spin Relaxation in GaAs Semiconductor Quantum Dots 233
8.2.3 Scalability 236
8.2.4 Switching 236
8.2.5 Quantum Error Correction 238
8.2.6 Gate Precision 239
8.2.7 Initialization 240
8.3 Coupled Quantum Dots as Quantum Gates 240
8.3.1 Lateral Coupling 241
8.3.2 Vertical Coupling 244
8.3.3 Anisotropic Exchange 245
8.3.4 Superexchange 247
8.3.5 Accessing the Exchange Interaction J Between the Spins in Coupled Quantum Dots Via the Kondo Effect 248
8.4 Single-Spin Rotations 250
8.4.1 Local Magnetic Coupling 251
8.4.2 Local g-Factor Coupling 251
8.4.3 Quantum Computing with Exchange Interactions Only 251
8.5 Read-Out of a Single Spin 253
8.5.1 Spontaneous Magnetization 253
8.5.2 Measuring Spin Via Charge 253
8.5.3 Coupled Dots as Entangler 254
8.5.4 Spin Filter 254
8.5.5 Berry Phase Controlled Spin Filter 255
8.5.6 Detection of Single-Spin Decoherence 256
8.5.7 Rabi Oscillations and Pulsed ESR 257
8.5.8 Spin Read-Out 258
8.5.9 Optical Measurements 259
8.6 Quantum Information Processing with Large-Spin Systems 259
8.7 Quantum Communication 260
8.7.1 Andreev Entangler 261
8.7.2 Andreev Entangler with Luttinger Liquid Leads 264
8.7.3 Entangled Electrons in a Fermi Sea 265
8.7.4 Noise of Entangled Electrons 266
8.7.5 Double-Dot with Normal Leads 268
8.7.6 Double-Dot with Superconducting Leads 269
8.7.7 Biexcitons in Coupled Quantum Dots as a Source of Entangled Photons and Electrons 270
8.8 Conclusions 272
9 Regulated Single Photons and Entangled Photons From a Quantum Dot Microcavity
Yoshihisa Yamamoto,Matthew Pelton,Charles Santori, Glenn S.Solomon,Oliver Benson,Jelena Vuckovic,and Axel Scherer 277
9.1 Introduction 277
9.2 Single InAs/GaAs Quantum Dots 279
9.3 Generation of Single Photons 285
9.4 Coupling Single Quantum Dots
to Micropost Microcavities 286
9.5 Theoretical Analysis of a Micropost DBR Cavity 293
9.6 Entangled Photon-Pairs
from a Single Quantum Dot 298
9.7 Conclusions 303
Index 307
END
