A unifying phase diagram with correlation-driven superconductor-to-insulator transition for the122☆series of iron chalcogenides
| Autor: | X. H. Niu, Hangdong Wang, Minghu Fang, Juan Jiang, Zhengzong Sun, Yajun Yan, D. F. Xu, Dachun Gu, Sudi Chen, Z. R. Ye, Jiangping Hu, Luchao Sun, Yu Feng, Donglai Feng, Binping Xie, Tianlun Yu, Min Xu, Qianhui Mao, Changjin Zhang, Jun Zhao |
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| Rok vydání: | 2016 |
| Předmět: |
Physics
Superconductivity Photoemission spectroscopy Star (game theory) Fermi surface 02 engineering and technology Electronic structure 021001 nanoscience & nanotechnology 01 natural sciences Crystallography 0103 physical sciences 010306 general physics 0210 nano-technology Ground state Pnictogen Phase diagram |
| Zdroj: | Physical Review B. 93 |
| ISSN: | 2469-9969 2469-9950 |
| Popis: | The ${122}^{\ensuremath{\star}}$ series of iron chalcogenide superconductors, for example ${\mathrm{K}}_{x}{\mathrm{Fe}}_{2\ensuremath{-}y}{\mathrm{Se}}_{2}$, only possesses electron Fermi pockets. Their distinctive electronic structure challenges the picture built upon iron pnictide superconductors, where both electron and hole Fermi pockets coexist. However, partly due to the intrinsic phase separation in this family of compounds, many aspects of their behavior remain elusive. In particular, the evolution of the ${122}^{\ensuremath{\star}}$ series of iron chalcogenides with chemical substitution still lacks a microscopic and unified interpretation. Using angle-resolved photoemission spectroscopy, we studied a major fraction of ${122}^{\ensuremath{\star}}$ iron chalcogenides, including the isovalently ``doped'' ${\mathrm{K}}_{x}{\mathrm{Fe}}_{2\ensuremath{-}y}{\mathrm{Se}}_{2\ensuremath{-}z}{\mathrm{S}}_{z},{\mathrm{Rb}}_{x}{\mathrm{Fe}}_{2\ensuremath{-}y}{\mathrm{Se}}_{2\ensuremath{-}z}{\mathrm{Te}}_{z}$, and ${(\text{Tl},\mathrm{K})}_{x}{\mathrm{Fe}}_{2\ensuremath{-}y}{\mathrm{Se}}_{2\ensuremath{-}z}{\mathrm{S}}_{z}$. We found that the bandwidths of the low energy Fe $3d$ bands in these materials depend on doping; and more crucially, as the bandwidth decreases, the ground state evolves from a metal to a superconductor, and eventually to an insulator, yet the Fermi surface in the metallic phases is unaffected by the isovalent dopants. Moreover, the correlation-driven insulator found here with small band filling may be a novel insulating phase. Our study shows that almost all the known ${122}^{\ensuremath{\star}}\text{-series}$ iron chalcogenides can be understood via one unifying phase diagram which implies that moderate correlation strength is beneficial for the superconductivity. |
| Databáze: | OpenAIRE |
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