Research and Prospects of Iron‐Based Superconductors

Abstract

The discovery of a new superconductor, LaFeAsO1−xFx with a superconducting critical temperatureT,c, of 26 K in 2008, has quickly renewed interest in the exploration of iron‐based superconductors. More than 70 new superconductors have been discovered within several months, with the highest Tc of up to 55 K being observed in the SmFeAsO1−x compound. High Tcs have previously only been observed in cuprates; these new iron‐based superconductors have been added as second members of the high‐Tc family. The crystal structure of these compounds contains an almost 2D Fe–As layer formed by FeAs4 tetrahedrons, which can be separated by an oxide or metal layer that provides extra electrons to the Fe–As layer, and the itinerant iron 3d electrons form an antiferromagnetic (AFM) order state in the undoped parent compounds at around 100–200 K. Superconductivity can be induced by carrier doping, which destroys the AFM ground state. In this Review, the most recent findings on and basic experimental facts about this class of high‐Tc materials will be presented, including the various superconducting structures, the synthesis methods, the physical properties of the parent compounds, the doping methods that could produce superconductivity, pressure effects, and the prospects for this new iron‐based high‐Tc family.

Electronic band structure and Fermi surface of new low-temperature Ni-based superconductors: 3.3K (Ni2P2)(Sr4Sc2O6) and 2.7K (Ni2As2)(Sr4Sc2O6) from first principles

“…In the band structure of (Ni 2 P 2 )(Sr 4 Sc 2 O 6 ), two lowest bands lying around - Sm, Dy, Gd, and A are alkali earth metals Ca, Sr, and Ba), for which at least three different competing types of magnetic fluctuations have been predicted, reviews [8][9][10][11][12][13].…”

“…The discovery of superconductivity in the layered iron pnictides (so-called 1111, 122, and 111 phases) [1][2][3][4][5][6] and iron chalcogenides Fe-Se(Te) [7] stimulated much activity in search for new related superconductors (SCs), reviews [8][9][10][11][12][13]. Recently, a new group of more complex five-component phases, namely iron pnictide oxides with general stoichiometry (Fe 2 Pn 2 )(A 4 M 2 O 6 ) (where Pn are pnictogens, and A and M are alkaline-earth and transition metals, respectively) has been discovered, and some physical properties of (Fe 2 Pn 2 )(A 4 M 2 O 6 ) phases have been examined both experimentally and theoretically, review [14].…”

Specific heat jump of two-band superconductor KFe2As2 using Ginzburg-Landau theory

“…In the spatially separated Fe layers electrons condense into Cooper pairs and the oxygen layers supply charge carriers in the case of deviation from stoichiometric composition. Detailed reviews * E-mail: Iman.Askerbeyli@eng.ankara.edu.tr of the state of the art investigations of these materials are given in [9][10][11][12][13]. Comparison of the properties of cuprate superconductors and Fe-based superconductors reveals that there are certain elements of similarities as well as many differences.…”

Elastic properties and inter-atomic bonding in new superconductor from first principles calculations

“…In this context, the elastic properties of 122-like FeSe phases seem important for various possible applications of these new superconducting materials, as well as can provide some hints on the difference or common features between well known 122 iron-pnictides (reviews [17][18][19][20][21]) and these new iron-selenide systems, and further shed light on the mechanism of superconductivity in Febased superconductors. Indeed, the elastic constants can be linked to such important physical parameters of superconductors (SCs) as the Debye temperature Θ D and the electron-phonon coupling constant λ [22].…”