FeSe superconductors and their related systems have attracted much attention in the study of iron-based superconductors owing to their simple crystal structure and peculiar electronic and physical properties. The bulk FeSe superconductor has a superconducting transition temperature ( T c) of ~8 K and it can be dramatically enhanced to 37 K at high pressure.

The Fermi Gamma-ray Space Telescope, formerly GLAST, is opening this high-energy world to exploration and helping us answer these questions. With Fermi, astronomers at long last have a superior tool to study how black holes, notorious for pulling matter in, can accelerate jets of gas outward at fantastic speeds. The international team who built and operate the Large Area Telescope, one of two instruments on the Fermi Gamma-ray Space Telescope (often known simply as Fermi), will have a meeting at CERN (the European particle accelerator facility that runs the Large Hadron Collider).

On the other hand, its cousin system, FeTe, possesses a unique antiferromagnetic ground state but is non-superconducting. Substitution of Se with Te in the FeSe superconductor results in an enhancement of T c up to 14.5 K and superconductivity can persist over a large composition range in the Fe(Se,Te) system. Intercalation of the FeSe superconductor leads to the discovery of the A xFe 2− ySe 2 (A = K, Cs and Tl) system that exhibits a T c higher than 30 K and a unique electronic structure of the superconducting phase. A recent report of possible high temperature superconductivity in single-layer FeSe/SrTiO 3 films with a T c above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high T c superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator–superconductor transition of the FeSe/SrTiO 3 films provide critical information in understanding the superconductivity mechanism of iron-based superconductors.

In this paper, we present a brief review of the investigation of the electronic structure and superconductivity of the FeSe superconductor and related systems, with a particular focus on the FeSe films. Export citation and abstract. Iron-based superconductors discovered in 2008 [] represent the second class of high temperature superconductors after the discovery of the first class of high- T c cuprate superconductors in 1986 []. The superconducting transition temperature ( T c) has reached ~55 K [–], which is beyond the generally-believed McMillan limit of the conventional superconductors.

Indications of even higher T c have emerged in single-layer FeSe films [–]. Driver kozumi k 5400pci v30 2017. Since the discovery of the cuprate superconductors, understanding the high temperature superconductivity mechanism remains a prominent and challenging task facing the condensed matter physics community. Deep freeze serial key 823. The discovery of iron-based superconductors provides an opportunity to compare and contrast with the cuprate superconductors that may help to uncover the secret to high temperature superconductivity. Great progress has been made in materials preparation, experimental investigation and theoretical understanding of iron-based superconductors [–]. So far, several families of iron-based superconductors have been discovered and can be mainly categorized into '11' [], '111' [], '122' [] and '1111' [, –] systems according to their crystal structure (figure ) []. Similar to cuprate superconductors, iron-based superconductors are quasi-two-dimensional in their crystal structure.

The FePn (Pn = As or Se) layer is an essential building block that is believed to be responsible for the superconductivity in iron-based superconductors. Different from the cuprate superconductors where the CuO 2 plane is basically co-planar, the FePn (Pn = As or Se) unit consists of three layers with the central Fe layer sandwiched in between two adjacent Pn layers. This results in the doubling of the unit cell in the iron-based superconductors and the folding of the corresponding electronic structure (figure ). Most significantly, different from cuprate superconductors where the low-energy physics is mainly dominated by the single Cu orbital, in iron-based superconductors, all the five Fe 3d orbitals participate in the low-energy electronic structures [–]. Generally, there are multiple bands crossing the Fermi level that form hole-like Fermi surface sheets near the Brillouin zone center and electron-like Fermi surface sheets near the zone corner [–]. The multiple-orbital nature (figure ) [, ] plays an important role in understanding the physical properties and superconductivity mechanism in iron-based superconductors. Brillouin zones of iron-based superconductors containing one iron and two irons in a unit cell and the orbital-related electronic structure.