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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. 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.

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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 []. Free download krisdayanti menghitung hari. 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 [–]. 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. 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 ).