Emin provides experimental and theoretical graduate students and researchers with a distinctive introduction to the principles governing polaron science. The fundamental physics is emphasized and mathematical formalism is avoided. The book gives a clear guide to how different types of polaron form and the measurements used to identify them. Analyses of four diverse physical problems illustrate polaron effects producing dramatic physical phenomena. The first part of the book describes the principles governing polaron and bipolaron formation in different classes of materials. The second part emphasizes distinguishing electronic-transport and optical phenomena through which polarons manifest themselves. The book concludes by extending polaron concepts to address critical aspects of four multifaceted electronic and atomic problems: large bipolarons' superconductivity, electronic switching of small-polaron semiconductors, electronically stimulated atomic desorption and diffusion of light interstitial atoms.

Preface page ix

Acknowledgments xvi

1 Succinct overview 1

Part I Polaron Formation 7

2 Electron–phonon interactions 9

2.1 Long-range electron–phonon interaction 9

2.2 Short-range electron–phonon interactions 11

3 Weak-coupling polarons: carrier-induced softening 13

3.1 Long-range electron–phonon interaction 13

3.2 Short-range electron–phonon interactions 14

3.3 Two-site model: origin of carrier-induced softening 15

4 Strong coupling: self-trapping 21

4.1 Adiabatic formalism 21

4.2 Self-trapping 23

4.3 Scaling approach: large- and small-polaron formation 29

4.4 Self-trapping beyond the adiabatic limit 33

4.5 Disorder-assisted small-polaron formation 39

4.6 Synopsis 41

5 Dopant- and defect-related small polarons 43

5.1 Small polarons bound to dopants and defects 43

5.2 Small-polaronic impurity conduction 45

6 Molecular polarons 49

6.1 General features 49

6.2 Examples 52

7 Bipolarons 54

7.1 Large-bipolaron formation 55

7.2 Small-bipolarons: negative-U centers 58

7.3 Softening bipolarons 59

8 Magnetic polarons and colossal magnetoresistance 65

8.1 Magnetic polarons 66

8.2 Donor-state collapse in ferromagnets: colossal magnetoresistance 68

Part II Polaron Properties 73

9 Optical properties 75

9.1 Absorption from exciting polarons' self-trapped carriers 75

9.2 Low-frequency absorption from polaron motion 78

9.3 Carriers' photo-generation, recombination and luminescence 81

10 Large-polaron transport 86

10.1 Coherent versus incoherent transport 86

10.2 Large-polaron effective mass 88

10.3 Large-polaron scattering 91

11 Small-polaron transport 95

11.1 Loss of coherence and hopping transport 95

11.2 Two complementary types of hopping transport 96

11.3 Overview of polaron hopping 98

11.4 Non-adiabatic polaron jump rate 102

11.5 Semiclassical treatment of the non-adiabatic polaron jump rate 108

11.6 Semiclassical treatment of the adiabatic polaron jump rate 110

11.7 Vibrational relaxation and correlations between polaron jumps 118

11.8 Pair-breaking in semiclassical singlet-bipolaron hopping 121

11.9 Exchange interactions and polaron hopping in magnetic semiconductors 123

12 Polarons' Seebeck coefficients 125

12.1 Definitions and general concepts 125

12.2 Hopping polarons' Seebeck coefficients 127

12.3 Softening (bi)polarons' Seebeck coefficients 129

12.4 Seebeck coefficients of polarons in magnetic semiconductors 133

13 Polarons' Hall effect 135

13.1 Coherent transport' s Hall mobility 136

13.2 Microscopic treatment of electric and magnetic fields 138

13.3 Hall mobility for non-adiabatic polaron hopping 140

13.4 Hall mobility for adiabatic polaron hopping 147

13.5 Hall-effect signs for hopping conduction 155

Part III Extending Polaron Concepts 161

14 Superconductivity of large bipolarons 163

14.1 Interactions between large bipolarons 164

14.2 Condensation to a large-bipolaronic liquid 165

14.3 Superconductivity and excitations of a large-bipolaronic liquid 167

14.4 Distinctive properties of a large-bipolaronic superconductor 168

15 Non-Ohmic hopping conduction and electronic switching 173

15.1 Formalism for steady-state hopping 173

15.2 Low-temperature hopping in a disordered medium 175

15.3 Interfacial small-polaron accretion: a threshold switching mechanism 180

16 Electronically stimulated desorption of atoms from surfaces 186

16.1 Model Hamiltonian 187

16.2 Scaling analysis 189

17 Hopping of light atoms 191

17.1 High-temperature diffusion: excited coincidences and non-Condon transfers 191

17.2 Isotope dependences of light-atoms' high-temperature diffusion constants 193

17.3 Isotope dependences of light-atoms' low temperature diffusion constants 196

References 198

Index 209

David Emin retired from Sandia National Laboratories and is currently Adjunct Professor in the Department of Physics and Astronomy, University of New Mexico. He is best known for his work on polaron formation and motion and is often cited for his seminal contributions to the theories of self-trapping and hopping conduction's phonon-assisted transition rates, Hall Effect and Seebeck Effect.

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