Electronic structure and superconductivity of FeSe-related superconductors

Abstract

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 (Tc) 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 Tc 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 AxFe2-ySe2 (A = K, Cs and Tl) system that exhibits a Tc 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/SrTiO3 films with a Tc above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high Tc superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator-superconductor transition of the FeSe/SrTiO3 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.

Discovery of orbital-selective Cooper pairing in FeSe

“…This deviation initially cast doubt on the scenario of spin-fluctuation driven nematicity, but recent experiments show that it is still the most likely candidate [44]. [45]. B, Phase diagram as a function of pressure.…”

Temperature Dependence of the Electronic Structure of FeSe

“…Слід відзначити, що найбільші ін-терес та увагу привертає електронна структура FeSe -найпрості-шого надпровідника на основі заліза, що приховує потенціял різко-го збільшення температури надпровідного переходу, який реалізу-ється під тиском або в моношаровій плівці. Кристалічна структура FeSe є досить простою та складається лише з шарів FeSe, який є од-ним з елементарних будівельних блоків для залізовмісних надпро-відників, тому така структура є особливо зручною для теоретичних та експериментальних досліджень механізмів надпровідности у Fe-ÍП [4][5][6][7].…”

Robustness of s-wave pairing symmetry in iron-based superconductors and its implications for fundamentals of magnetically driven high-temperature superconductivity

“…1(a) and (b), a direct measurement of the gap functions on the hole pockets can determine the pairing symmetry. The angle resolved photoemission spectroscopy (ARPES) has been employed to measure a variety of iron-based superconductors [15,26] that exhibit hole pockets at the zone center, including hole doped Ba 2−x K x Fe 2 As 2 , electron doped Li(Na)Fe 1−x Co x As, isovalent doped BaFe 2 (As 1−x P x ) 2 and BaFe 2−x Ru x As 2 , and FeSe 1−x Te x . There are two common results regarding the measured gap functions of the hole pockets.…”