Iron Based Superconductors: Pnictides versus Chalcogenides

Abstract

We present a brief review of the present day situation with studies of high-temperature superconductivity in iron pnictides and chalcogenides. Recent discovery of superconductivity with T_c > 30 K in A_xFe_{2-x/2}Se_2 (A=K,Cs,Tl,...) represents the major new step in the development of new concepts in the physics of Fe - based high-temperature superconductors. We compare LDA and ARPES data on the band structure and Fermi surfaces of novel superconductors and those of the previously studied FeAs superconductors, especially isostructural 122 - superconductors like BaFe_2As_2. It appears that electronic structure of new superconductors is rather different from that of FeAs 122 - systems. In particular, no nesting properties of electron and hole - like Fermi surfaces is observed, casting doubts on most popular theoretical schemes of Cooper pairing for these systems. The discovery of Fe vacancies ordering and antiferromagnetic (AFM) ordering at pretty high temperatures (T_N> 500 K), much exceeding superconducting T_c makes these systems unique antiferromagnetic superconductors with highest T_N observed up to now. We discuss the role of both vacancies and AFM ordering in transformations of band structure and Fermi surfaces, as well as their importance for superconductivity. In particular, we show that system remains metallic with unfolded Fermi surfaces quite similar to that in paramagnetic state. Superconducting transition temperature T_c of new superconductors is discussed within the general picture of superconductivity in multiple band systems. It is demonstrated that both in FeAs - superconductors and in new FeSe - systems the value of T_c correlates with the value of the total density of states (DOS) at the Fermi level.

6 pages, 7 figures, talk to be given at Moscow International Symposium on Magnetism (MISM-2011), August 21-25, 2011

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Cited by in corpus (18)

• Electron pairing in the presence of incipient bands in iron-based superconductors
• Electronic band structure of ferro-pnictide superconductors from ARPES experiment
• Electronic structure of FeSe monolayer superconductors
• The electron-phonon interaction with forward scattering peak is a relevant approach to high Tc superconductivity in FeSe films on SrTiO3 and TiO2
• Evolution of the multiband RKKY interaction: Application to iron pnictides and chalcogenides
• Electronic structure of NaFeAs superconductor: LDA+DMFT calculations compared with ARPES experiment
• Electronic structure of FeSe monolayer superconductors: shallow bands and correlations
• Electronic structure of iron-based superconductors: from pnictides to chalcogenides and other similar systems
• On the origin of the shallow and "replica" bands in FeSe monolayer superconductors
• LDA'+DMFT Investigation of Electronic Structure of K{1-x}Fe{2-y}Se2 Superconductor
• Electronic and Magnetic Properties of the New Iron -- Based Superconductor [Li${}_{1-x}$Fe${}_x$OH]FeSe
• Interplay of superconductivity and magnetism in FeSe${}_{1-x}$Te${}_x$ compounds. Pressure effects
• Doping Dependence of Correlation Effects in K{1-x}Fe{2-y}Se2 Superconductor: LDA'+DMFT Investigation
• Comparative Study of Electronic structure of New Superconductors (Sr,Ca)Pd2As2 and related compound BaPd2As2
• Weakness of Correlation Effect Manifestation in BaNi${}_2$As${}_2$: ARPES and LDA+DMFT study
• Thermodynamics of $s_{\pm }-to-s_{++}$ transition in iron pnictides in the vicinity of the Born limit
• Hidden Fermi surface in K${}_x$Fe${}_{2-y}$Se${}_2$: LDA+DMFT study
• Critical point of the transition between $s_{\pm }$ and $s_{++}$ states of a two-band superconductor with nonmagnetic impurities