Crystal structure of the new FeSe1−x superconductor

Margadonna, Serena; Takabayashi, Yasuhiro; McDonald, Martin T.; Kasperkiewicz, Karolina; Mizuguchi, Yoshikazu; Takano, Yoshihiko; Fitch, Andrew N.; Suard, Emmanuelle; Prassides, Kosmas

doi:10.1039/b813076k

Cited by 337 publications

(367 citation statements)

References 15 publications

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“…Superconductivity in these materials has been discovered in 2008 by Hosono and his collaborators [24]. Later, superconductivity has been found also in Fe-chalcogenides -Fe-based compounds with elements from the 16th group: S, Se, Te [59,60,61,62].…”

Section: Superconductivity In Fe-pnictidesmentioning

confidence: 99%

Superconductivity from repulsive interaction

Maiti¹,

Chubukov²

2014

Novel Superfluids

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Abstract. The BCS theory of superconductivity named electron-phonon interaction as a glue that overcomes Coulomb repulsion and binds fermions into pairs which then condense and super-conduct. We review recent and not so recent works aiming to understand whether a nominally repulsive Coulomb interaction can by itself give rise to a superconductivity. We first discuss a generic scenario of the pairing by electron-electron interaction, put forward by Kohn and Luttinger back in 1965, and then turn to modern studies of the electronic mechanism of superconductivity in the lattice models for the cuprates, the Fe-pnictides, and the doped graphene. We show that the pairing in all three classes of materials can be viewed as lattice version of Kohn-Luttinger physics, despite that the pairing symmetries are different. We discuss under what conditions the pairing occurs and rationalize the need to do parquet renormalization-group analysis. We also discuss the interplay between superconductivity and density-wave instabilities.

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Section: Superconductivity In Fe-pnictidesmentioning

confidence: 99%

Superconductivity from repulsive interaction

Maiti¹,

Chubukov²

2014

Novel Superfluids

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“…For the Fe 1+x (Te-Se) system [9,[30][31][32][33], crystallographically there are two iron sites, one of which is partially occupied, while the (Te, Se) site is fully occupied. Hence the composition should be indicated as Fe 1+x (Te,Se).…”

Section: Fe 1+x (Te-se) Systemmentioning

confidence: 99%

Neutron studies of the iron-based family of high TC magnetic superconductors

Lynn

Dai

2009

Physica C: Superconductivity

154

163

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We review neutron scattering investigations of the crystal structures, magnetic structures, and spin dynamics of the iron-based RFe(As,P)O (R=La, Ce, Pr, Nd), (Ba,Sr,Ca)Fe 2 As 2 , and Fe 1+x (Te-Se) systems. On cooling from room temperature all the undoped materials exhibit universal behavior, where a tetragonal-to-orthorhombic/monoclinic structural transition occurs, below which the systems become antiferromagnets. For the first two classes of materials the magnetic structure within the a-b plane consists of chains of parallel Fe spins that are coupled antiferromagnetically in the orthogonal direction, with an ordered moment typically less than one Bohr magneton. Hence these are itinerant electron magnets, with a spin structure that is consistent with Fermi-surface nesting and a very energetic spin wave bandwidth ~0.2 eV. With doping, the structural and magnetic transitions are suppressed in favor of superconductivity, with superconducting transition temperatures up to ≈55 K. Magnetic correlations are observed in the superconducting regime, with a magnetic resonance that follows the superconducting order parameter just like the cuprates. The rare-earth moments order antiferromagnetically at low T like 'conventional' magnetic-superconductors, while the Ce crystal field linewidths are affected when superconductivity sets in. The application of pressure in CaFe 2 As 2 transforms the system from a magnetically ordered orthorhombic material to a 'collapsed' non-magnetic tetragonal system. Tetragonal Fe 1+x Te transforms to a low T monoclinic structure at small x that changes to orthorhombic at larger x, which is accompanied by a crossover from commensurate to incommensurate magnetic order.Se doping suppresses the magnetic order, while incommensurate magnetic correlations are observed in the superconducting regime.

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“…Consequently, the issue of nematicity is more crucially posed for those systems where the structural transition precedes the magnetic one (T S T N ), leaving a finite temperature interval where C 4 symmetry is broken but the material remains paramagnetic [9][10][11][12]. The most notable example being FeSe where only a structural transition [13,14] is detected (the difference between the T s and T N being the largest) and the system remains paramagnetic till its SC phase [15,16], indicating that nematic degrees of freedom are not necessarily magnetic ones but probably orbital one. The microscopic origin of the nematic order is debatable with a few competitive probable scenarios [17].…”

Section: Introductionmentioning

confidence: 99%

Electronic origin of structural transition in 122 Fe based superconductors

Ghosh

Sen

Ghosh

2017

Journal of Physics and Chemistry of Solids

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Direct quantitative correlations between the orbital order and orthorhombicity is achieved in a number of Fe-based superconductors of 122 family. The former (orbital order) is calculated from first principles simulations using experimentally determined doping and temperature dependent structural parameters while the latter (the orthorhombicity) is taken from already established experimental studies; when normalized, both the above quantities quantitatively corresponds to each other in terms of their doping as well as temperature variations. This proves that the structural transition in Fe-based materials is electronic in nature due to orbital ordering. An universal correlations among various structural parameters and electronic structure are also obtained. Most remarkable among them is the mapping of two Fe-Fe distances in the low temperature orthorhombic phase, with the band energies E dxz , E dyz of Fe at the high symmetry points of the Brillouin zone. The fractional co-ordinate zAs of As which essentially determines anion height is inversely (directly) proportional to Fe-As bond distances (with exceptions of K doped BaFe2As2) for hole (electron) doped materials as a function of doping. On the other hand, Fe-As bond-distance is found to be inversely (directly) proportional to the density of states at the Fermi level for hole (electron) doped systems. Implications of these results to current issues of Fe based superconductivity are discussed.

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Crystal structure of the new FeSe1−x superconductor

Cited by 337 publications

References 15 publications

Superconductivity from repulsive interaction

Superconductivity from repulsive interaction

Neutron studies of the iron-based family of high TC magnetic superconductors

Electronic origin of structural transition in 122 Fe based superconductors

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