Presenting an up-to-date report on electronic glasses, this book examines experiments and theories for a variety of disordered materials where electrons exhibit glassy properties. Some interesting mathematical models of idealized systems are also discussed. The authors examine problems in this field, highlighting which issues are currently understood and which require further research. Where appropriate, the authors focus on physical arguments over elaborate derivations. The book provides introductory background material on glassy systems, properties of disordered systems and transport properties so it can be understood by researchers in condensed matter physics who are new to this field.

Acknowledgments page ix

List of symbols x

1 Introduction 1

2 Disordered electronic systems 7

2.1 Disordered solids 7

2.2 Hamiltonians for disordered systems 11

2.3 Strong disorder 13

2.4 Weak disorder 18

2.5 Anderson localization and metal–insulator transitions 23

2.6 Percolation theory 34

3 Basics of glasses 40

3.1 The modern concept of glass 40

3.2 The glass transition 41

3.3 Types of glasses 43

3.4 Ergodicity 44

3.5 The fluctuation–dissipation theorem 45

3.6 Aging 48

3.7 Spin glasses 50

3.8 Two-site systems 57

4 Equilibrium properties of the electron glass 60

4.1 The model Hamiltonian for strong localization 61

4.2 Density of states: the Coulomb gap 63

4.3 Numerical simulations 73

4.4 Interactions and Anderson localization 86

5 dc Conductivity 92

5.1 dc Conductivity: experimental 92

5.2 Elements of the theory of hopping transport 98

5.3 Variable range hopping 115

5.4 Percolation approach to hopping conduction 119

5.5 Scaling theory of transport 125

5.6 Numerical simulations 132

5.7 Concluding remarks 137

6 Other transport properties of electron glasses 139

6.1 High field conductivity 139

6.2 Magnetoresistance 145

6.3 Hall effect 154

6.4 ac Conductivity 157

6.5 1/f Noise 168

6.6 Mesoscopic effects 176

7 Glassy behavior 182

7.1 The nature of the phase space 183

7.2 Glassy relaxation 185

7.3 Models for logarithmic relaxation 206

7.4 Numerical simulations of relaxation 216

7.5 Aging 224

7.6 Memory – two dip experiment 234

7.7 Coexistence of mesoscopic and glassy effects 237

7.8 Details of specific electron glasses 239

7.9 Concluding remarks 252

8 Relationship to other glasses 253

8.1 Structural glasses 253

8.2 Dipole glasses 256

8.3 Spin glasses 257

8.4 Vortex glass 260

9 Open issues 264

References 269

Index 289

A. Frydman is a Professor of Physics and heads the nano-electronic laboratory in Bar-Ilan University, Israel. He is an expert in experimental research of the electronic properties of low

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