The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c = 26 K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic. In short order, ot...

The puzzle of high temperature superconductivity in layered iron pnictides and chalcogenides

The surprising discovery of high-temperature superconductivity in a material containing a strong magnet—iron—has led to thousands of publications. By placing all the data in context, it becomes clear what we know and where we are headed.

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High-temperature superconductivity in iron-based materials

Point-contact spectroscopy was originally developed for the determination of the electron–phonon spectral function in normal metals. However, in the past 20 years it has become an important tool in the investigation of superconductors. As a matter of fact, point contacts between a normal metal and a superconductor can provide information on the amplitude and symmetry of the energy gap that, in the superconducting state, opens up at the Fermi level. In this paper we review the experimental and theoretical aspects of point-contact spectroscopy in superconductors, and we give an experimental survey of the most recent applications of this technique to anisotropic and multiband superconductors.

https://iopscience.iop.org/article/10.1088/0953-2048/23/4/043001/pdf

Probing multiband superconductivity by point-contact spectroscopy

Angle-resolved photoemission spectroscopy (ARPES) — an experimental technique based on the photoelectric effect — is arguably the most powerful method for probing the electronic structure of solids. The past decade has witnessed notable progress in ARPES, including the rapid development of soft-X-ray ARPES, time-resolved ARPES, spin-resolved ARPES and spatially resolved ARPES, as well as considerable improvements in energy and momentum resolution. Consequently, ARPES has emerged as an indispensable experimental probe in the study of topological materials, which have characteristic non-trivial bulk and surface electronic structures that can be directly detected by ARPES. Over the past few years, ARPES has had a crucial role in several landmark discoveries in topological materials, including the identification of topological insulators and topological Dirac and Weyl semimetals. In this Technical Review, we assess the latest developments in different ARPES techniques and illustrate the capabilities of these techniques with applications in the study of topological materials. Angle-resolved photoemission spectroscopy (ARPES) is a tool for directly probing the electronic structure of solids and has had a crucial role in studying topological materials. In this Technical Review, we discuss the latest developments of various ARPES techniques and their applications to topological materials

Angle-resolved photoemission spectroscopy and its application to topological materials

Angle-resolved photoemission spectroscopy allows direct visualization and experimental determination of the electronic structure of crystals in the momentum space, including the precise characterization of the Fermi surface and the superconducting order parameter. It is thus particularly suited for investigating multi-band systems such as the Fe-based superconductors. In this review, we cover several aspects of these recently discovered materials that have been addressed by this technique, with a special emphasis on their superconducting gap and their Fermi surface topology. We provide sufficient experimental evidence to support the reliability and the consistency of the angle-resolved photoemission spectroscopy measurements over a wide range of material compositions.

https://iopscience.iop.org/article/10.1088/0034-4885/74/12/124512/pdf

Fe-based superconductors: an angle-resolved photoemission spectroscopy perspective

The electronic structure of electron doped iron-arsenide superconductors Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} has been measured with Angle Resolved Photoemission Spectroscopy. The data reveal a marked photon energy dependence of points in momentum space where the bands cross the Fermi energy, a distinctive and direct signature of three-dimensionality in the Fermi surface topology. By providing a unique example of high temperature superconductivity hosted in layered compounds with three-dimensional electronic structure, these findings suggest that the iron-arsenides are unique materials, quite different from the cuprates high temperature superconductors.

Evidence for three-dimensional Fermi-surface topology of the layered electron-doped iron superconductor Ba(Fe1 xCox)2As2

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Athena Safa-Sefat

Papers

Evidence for three-dimensional Fermi-surface topology of the layered electron-doped iron superconductor Ba(Fe1 xCox)2As2

Direct Probe of Interplay between Local Structure and Superconductivity in FeTe0.55Se0.45