1 Introduction 1
2 Compounds of the ReOFeAs Type 5
2.1 Crystallochemistry and Basic Physical Properties of Doped Compounds 5
2.1.1 Crystal Structure 5
2.1.2 Electron Doping 5
2.1.3 Hole Doping 8
2.1.4 Substitutions on the Fe Sublattice 9
2.1.5 Superconducting Transition Temperature 11
2.1.6 CriticalFields 13
2.1.7 Effect of Pressure on the Tc 14
2.2 Magnetic Properties 18
2.2.1 Magnetic Structure 18
2.2.2 Theoretical Explanation of Long-Range Magnetic Ordering in ReOFeAs 20
2.2.3 PhaseDiagrams 24
2.2.4 Magnetic Fluctuations 27
2.3 Electronic Structure 28
2.3.1 Stoichiometric Compounds 28
2.3.2 The Role of Magnetic Ordering and Doping 34
2.3.3 Experimental Studies of the Fermi Surface 38
2.4 Symmetry of the Superconducting Order Parameter 41
2.4.1 Experimental Methods of Determining the Order Parameter 41
2.4.2 Nuclear Magnetic Resonance 42
2.4.3 Point-Contact Andreev Reflection 46
2.4.4 Tunnel and Photoemission Spectroscopies(STS,PES,ARPES) 53
3 Compounds of the AFe2As2(A=Ba,Sr,Ca)Type 57
3.1 Crystal and Electronic Structure 57
3.1.1 Crystal Structure 57
3.1.2 LDACalculations of the Electronic Structure 58
3.1.3 Experimental Studies of the Fermi Surface 63
3.1.4 (Sr3Sc2O5)Fe2As2 and Other Similar Compounds 69
3.2 Superconductivity 72
3.2.1 Doping 72
3.2.2 Coexistence of Superconductivity and Magnetism 77
3.2.3 Effect of Pressure 79
3.2.4 Symmetry of the Superconducting Order Parameter 88
3.2.5 Measurements on the Josephson Contacts 94
3.2.6 Critical Fields 96
3.3 Magnetism 98
3.3.1 Stoichiometric Compounds 98
3.3.2 DopedCompounds 102
3.3.3 MagneticExcitations 104
4 Other FeAs-Based Compounds 109
4.1 Compounds of the FeSe,FeTe Type 109
4.1.1 Superconducting Properties 109
4.1.2 Unusual Magnetic Properties 112
4.1.3 Electronic Structure of Stoichiometric Compounds 115
4.1.4 Electronic Structure of Doped Compounds 118
4.1.5 Magnetic Structure of FeTe 120
4.2 Compounds of the LiFeAs Type 122
4.2.1 Superconductivity 122
4.2.2 Electronic Structure 123
4.3 Compounds of the AFFeAs(A=Sr,Ca)Type 126
4.3.1 Primary Experimental Observations 126
4.3.2 Electronic Structure 128
5 Theory Models 131
5.1 General Properties of Compounds from Different Classes of FeAs-Systems and Corresponding Theory Objectives 131
5.1.1 Crystal and Magnetic Structures 131
5.1.2 Peculiarities of the Electronic Structure 134
5.1.3 Asymmetry of the Electron/Hole Doping 136
5.1.4 Problems of Symmetry of the Superconducting Order Parameter 138
5.1.5 Isotopic Effect 140
5.2 Role of Electron Correlations 141
5.2.1 Dynamical Mean Field Theory(DMFT) 141
5.2.2 LDA+DMFT Calculation for ReOFeAs Compounds 145
5.2.3 LDA+DMFT Calculation on an Extended Basis 148
5.2.4 Comparison with Experiment 152
5.3 A Minimal Two-Orbital Model 158
5.3.1 Formulation of the Model 158
5.3.2 Band Structure of the Spectrum 162
5.3.3 Mean Field Approximation 164
5.3.4 Numerical Calculation for Small Clusters 167
5.4 Multi-Orbital Model 170
5.4.1 Formulation of the Model 170
5.4.2 Equations for a Superconductor in the Fluctuation Exchange(FLEX)Approximation 171
5.4.3 Properties of Superconductors with the s？ Symmetry of the Order Parameter 174
5.4.4 Three-Orbital Model 178
5.5 Detailed Analysis of the 5-Orbital Model 182
5.5.1 The Hamiltonian of the Model 182
5.5.2 Spin and Charge Susceptibility 184
5.5.3 Pairing of Electrons via Spin Fluctuations 187
5.5.4 Possible Symmetries of the Superconducting Order Parameter 190
5.6 Limit of Weak Coulomb Interaction 194
5.6.1 Renormalization Group Analysis 194
5.6.2 Equations for Superconducting and Magnetic Order Parameters 202
5.6.3 Phase Diagram of the Model 205
5.6.4 Peculiarities of the s？-Superconducting State 207
5.7 The Limit of Strong Coulomb Interaction 210
5.7.1 The t-J1-J2-Model 210
5.7.2 Superconductivity with Different Order Parameters 212
5.7.3 Density of States and Differential Tunnel Conductivity 215
5.7.4 The Hubbard Model with the Hund's Exchange 217
5.8 Magnetic Long-Range Order and Its Fluctuations 221
5.8.1 Two Approaches to the Problem 221
5.8.2 The Itinerant Model 224
5.8.3 The Localized Model：Spin Waves 228
5.8.4 The Resonance Mode 233
5.8.5 Unified Models 240
5.8.6 FeAs-Compounds as Systems with Moderate Electron Correlations 245
5.9 Orbital Ordering 247
5.9.1 The Spin-Orbital Model 247
5.9.2 Phase Diagrams with Spin and Orbital Orderings 250
5.9.3 Spectrum of Magnetic Excitations 251
Conclusion 255
References 259
Index 277