Topological quantum states of matter in iron-based superconductors: from concept to material realization

Abstract

We review recent progress in the explorations of topological quantum states of matter in iron-based superconductors. In particular, we focus on the nontrivial topology existing in the band structures and superconducting states of iron's 3d orbitals. The basic concepts, models, materials and experimental results are reviewed. The natural integration between topology and high-temperature superconductivity in iron-based superconductors provides great opportunities to study topological superconductivity and Majorana modes at high temperature.

On the Remarkable Superconductivity of FeSe and Its Close Cousins

“…In the resulting band structure, the inverted parity-exchanged hole (electron) bands acquire p z /d xy (d xz /d yz ) orbital weight. For further details about the generations of topological bands in FeSCs monolayers, we refer to references [261,376] and recent reviews in references [25,67].…”

“…Together with the rough consensus on many aspects of Fe-pnictide superconductivity, the challenges posed by these and other discoveries in the Fe-chalcogenide family suggest that the time is ripe to review developments in this field. Following reviews of mostly experimental results [22,23], a review focused on bulk FeSe [24], and recent specialized reviews of topological aspects [25,26], we attempt here to synthesize what has been learned about the Fe-chalcogenide superconductors, with an emphasis on the superconducting state. Our goal is to elucidate which new theoretical ideas have been stimulated by experimental discoveries, and highlight remaining open questions in the field.…”

Observation of topological transition in high- Tc superconducting monolayer FeTe1−xSex films on Peng1, Li2, Wu3 et al. 2019Phys. Rev. B471300View full textAdd to dashboardCite

“…Moreover, as shown above, the sample with Se content x = 0.21 is already close to the critical point. To visualize the band inversion process,7 we systematically study the band structure evolution of monolayer FeTe1-xSex as a function of the Se content x.Figures 3(a)-3(c) show the band structures of six different Se content samples detected by 22 eV p-, 32 eV p-and 32 eV s-polarized photons. With one particular photon energy, we…”

Exploring Topological Superconductivity in Topological Materials

“…The rich phases may be related to the multiorbital physics. Therefore, intrinsic hybridization of various bands could exist in these systems and contribute to band inversions similar to in TIs, which appeals to theorists, and nontrivial topological states in some iron‐based superconductors have been proposed …”