Mechanisms of Conventional and High Tc Superconductivity

by Vladimir Z. Kresin, Hans Morawitz, Stuart A. Wolf

Overview

Superconductivity has become one of the most intensely studied physical phenomena of our times, with tremendous potential to revolutionize fields as diverse as computing and transportation. This book describes the methods, established results, and recent advances in the field. The goal is to present recently developed theoretical models in light of the long-sought aim of achieving the effect at very high temperatures. The book includes a detailed review of various mechanisms, including phononic, magnetic, and electronic models. The authors focus on the phenomenon of induced superconductivity in the high-temperature oxides, particularly the high-transition-temperature cuprates. They also discuss a variety of low-temperature superconducting systems in conventional materials and organics. The book links the crucial experiments with the most current theories, offering a unified description of the phenomenon. All researchers (and graduate-level) students involved with work in superconductivity will find this an invaluable resource, including solid-state and condensed-matter physicists and chemists, and materials scientists.

Product Details

ISBN-13:	9780195363586
Publisher:	Oxford University Press
Publication date:	06/17/1993
Series:	International Series of Monographs on Physics , #84
Sold by:	Barnes & Noble
Format:	eBook
File size:	3 MB

About the Author

University of California, Berkeley

IBM Almaden Research Center, San Jose

Table of Contents

1.	Introduction	3
1.1	Major goals	3
1.2	Historical perspective	4
2.	Phonon Mechanism	6
2.1	Electron-phonon interaction	6
2.1.1	The Hamiltonian	6
2.1.2	Adiabatic approximation. "Crude" approach	7
2.1.3	Electron-phonon coupling	10
2.1.4	Superconductivity as a nonadiabatic phenomenon	13
2.2	Eliashberg equations. Superconductors with strong coupling	14
2.2.1	Self-energy parts	14
2.2.2	General properties of the Eliashberg equations	17
2.3	Critical temperature	20
2.3.1	Weak coupling	20
2.3.2	Intermediate coupling ([lambda] [less-than, similar] 1.5)	22
2.3.3	Coulomb interaction	24
2.3.4	Very strong coupling	25
2.3.5	General case	27
2.4	Properties of superconductors with strong coupling	30
2.5	Electron-phonon interaction and renormalization of normal parameters	34
2.6	Nonlinear electron-phonon interactions	37
2.6.1	Phonon dynamics of perovskites	37
2.6.2	Anharmonicity	39
2.6.3	Bipolaronic superconductivity and negative Hubbard U-models	41
2.7	Isotope effect	42
3.	Experimental Methods	44
3.1	Tunneling spectroscopy	44
3.1.1	Experimental methods	44
3.1.2	Energy gap and transition temperature	46
3.1.3	Inversion of the gap equation and [alpha superscript 2]F([Omega])	48
3.1.4	Electron-phonon coupling parameter [lambda]	50
3.2	Infrared spectroscopy	52
3.3	Ultrasonic attenuation	54
3.4	Nuclear magnetic resonance	55
4.	Electronic Mechanisms	58
4.1	The Little model	58
4.2	"Sandwich" excitonic mechanism	61
4.3	Excitons and high T[subscript c]	61
4.4	Three-dimensional systems	62
4.4.1	Pairing of conduction electrons via interaction with localized states	62
4.4.2	Two delocalized groups	63
4.5	Negative U-centers	64
4.6	Plasmons	65
4.6.1	Overlapping bands. "Demons"	65
4.6.2	Two-dimensional electron gas	68
4.7	Coexistence of phonon and electronic mechanisms	68
5.	Magnetic Mechanisms	71
5.1	Introduction	71
5.1.1	Localized vs. itinerant aspects of the cuprates	72
5.2	Fermi liquid-based theories	75
5.2.1	The spin bag model of Schrieffer, Wen, and Zhang	75
5.2.2	The t-J model	78
5.2.3	Two-dimensional Hubbard model studies by Monte Carlo techniques	83
5.2.4	Spiral phase of a doped quantum antiferromagnet	92
5.2.5	Slave bosons	97
5.3	Non-Fermi-liquid models	100
5.3.1	The resonant valence bond (RVB) model and its evolution	100
5.3.2	Anyon models and fractional statistics	101
5.4	Conclusions	102
6.	Induced Superconductivity	103
6.1	Two-band model	103
6.1.1	General description	103
6.1.2	Critical temperature	104
6.1.3	Two-gap spectrum and properties of superconductors	106
6.1.4	Induced two-band superconductivity	107
6.2	Proximity effect	108
6.2.1	Proximity "sandwich"	108
6.2.2	Critical temperature. Induced energy gap	109
6.3	Proximity effect vs. the two-gap model	112
6.4	Layered systems. General case	113
6.4.1	Hamiltonian. General equations	113
6.4.2	Critical temperature	116
6.4.3	Spectroscopy	123
6.4.4	Magnetic impurities. Gapless induced superconductivity	125
6.4.5	Major parameters	126
6.4.6	Conventional superconductors	126
7.	High T[subscript c] Cuprates	128
7.1	Introduction	128
7.2	Normal properties	129
7.2.1	One-particle excitations	129
7.2.2	Collective excitations	133
7.3	Superconducting properties	137
7.3.1	Coherence length	137
7.3.2	The ratio [varepsilon](0)/E[subscript F]	138
7.3.3	Critical behavior	138
7.3.4	Positron annihilation	139
7.3.5	Electromagnetic properties	140
7.4	Induced superconducting state and two-gap structure	142
7.4.1	Two-gap structure. Coherence lengths	143
7.4.2	Oxygen depletion and the gapless state	144
7.4.3	Bi- and Tl-based cuprates	146
7.5	Origin of high T[subscript c]	146
7.5.1	Determination of carrier--phonon coupling parameter	147
7.5.2	Critical temperature	149
7.5.3	Discussion	150
7.6	Key experiments	151
7.6.1	Normal properties	151
7.6.2	Superconducting properties	153
7.6.3	Properties as a function of doping	156
7.7	Organics vs. cuprates	159
7.7.1	Why is T[subscript c] still so low in the organics?	159
7.7.2	Superconducting fullerenes	161
7.8	Future directions	164
	References	166
	Index	179

Editorial Reviews

"The writing is clear and concise. There are plenty of figures in the description of experimental data. I recommend this book."—Superconductivity Review

From the Publisher