The orbital characters of low-energy electronic structure in iron-chalcogenide superconductor K
                x
              Fe2−y
              Se2

Chen, Fei; Ge, Q. Q.; Xu, Min; Zhang, Yan; Shen, Xiaoping; Li, Wei; Matsunami, Masaharu; Kimura, S.; Hu, Jiangping; Feng, D. L.

doi:10.1007/s11434-012-5405-7

Cited by 11 publications

(10 citation statements)

References 32 publications

(48 reference statements)

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“…1h,j ), indicating that the nematic order is suppressed 6 . Considering that this electronic structure is similar to that in other heavily electron-doped iron chalcogenides, the electronic states near Fermi energy in K-dosed FeSe should as well be contributed by electrons with d xz , d yz and d xy orbitals 31 . There is no band structure corresponding to an intermediate doping level, so we conclude that the electron doping induced by K dosing is confined to the topmost single-unit-cell layer of FeSe.…”

Section: Resultssupporting

confidence: 55%

Anomalous correlation effects and unique phase diagram of electron-doped FeSe revealed by photoemission spectroscopy

et al. 2016

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FeSe layer-based superconductors exhibit exotic and distinctive properties. The undoped FeSe shows nematicity and superconductivity, while the heavily electron-doped KxFe2−ySe2 and single-layer FeSe/SrTiO3 possess high superconducting transition temperatures that pose theoretical challenges. However, a comprehensive study on the doping dependence of an FeSe layer-based superconductor is still lacking due to the lack of a clean means of doping control. Through angle-resolved photoemission spectroscopy studies on K-dosed thick FeSe films and FeSe0.93S0.07 bulk crystals, here we reveal the internal connections between these two types of FeSe-based superconductors, and obtain superconductivity below ∼46 K in an FeSe layer under electron doping without interfacial effects. Moreover, we discover an exotic phase diagram of FeSe with electron doping, including a nematic phase, a superconducting dome, a correlation-driven insulating phase and a metallic phase. Such an anomalous phase diagram unveils the remarkable complexity, and highlights the importance of correlations in FeSe layer-based superconductors.

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Section: Resultssupporting

confidence: 55%

Anomalous correlation effects and unique phase diagram of electron-doped FeSe revealed by photoemission spectroscopy

et al. 2016

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“…(a) Doping dependence of the photoemission intensity distributions along the Γ-M direction in Rb x Fe 2−y Se 2−z Te z and K x Fe 2−y Se 2−z S z , and the corresponding second derivatives with respect to energy. The band structures were determined for the superconducting phases of these compounds[37]. The white double-headed arrows indicate the bandwidth of the β band.…”

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confidence: 99%

A unifying phase diagram with correlation-driven superconductor-to-insulator transition for the122☆series of iron chalcogenides

et al. 2016

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The 122 * series of iron-chalcogenide superconductors, for example K x Fe 2−y 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 * 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 * iron-chalcogenides, including the isovalently 'doped' K x Fe 2−y Se 2−z S z , Rb x Fe 2−y Se 2−z Te z and (Tl,K) x Fe 2−y Se 2−z 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 * -series iron chalcogenides can be understood via one unifying phase diagram which implies that moderate correlation strength is beneficial for the superconductivity.

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“…Figure 1(a) shows the resistance (R) as a function of temperature (T) for the undoped Rb-245 superconductor measured at different pressures. It can be seen that the R-T curve demonstrates a remarkable hump around 200 K. The resistance hump is suggested to have originated from the competition between the insulating AFM phase and the superconducting phase [27,28,36]. Upon increasing pressure, the hump is suppressed significantly, same as that seen in the pressurized K-245 and Tl(Rb)-245 superconductors [30,32].…”

Section: Resultsmentioning

confidence: 78%

“…Soon after, the superconductivity was also found in Rb-245 and Cs-245 compounds [10][11][12][13][14][15]. Then, the characteristics of lattice, electronic and magnetic structures have been widely reported for these superconductors, such as the existence of phase separation [16][17][18][19], the superlattice of ordered Fe vacancies and its connection to the AFM ordered phase [20][21][22][23], absence of hole pockets at the Fermi surface [24][25][26], temperature-induced orbital selection [27][28][29]. All of these features are shown neither in the iron arsenide nor in copper oxide superconductors, therefore the complexity of understanding its superconducting mechanism is raised to a new level.…”

Section: Introductionmentioning

confidence: 99%

Superconductivity in pressurized Rb_0.8Fe_2−ySe_2−xTe_x

Zhou

et al. 2015

New J. Phys.

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We report the finding of pressure-induced elimination and reemergence of superconductivity in Rb 0.8 Fe 2−y Se 2−x Te x (x = 0, 0.19 and 0.28) superconductors that belong to the family of A-245 superconductors (A = K, Rb, TlRb and Cs), characterized by the presence of an antiferromagnetic (AFM) long-ranged order phase with the superlattice structure of Fe-cavacies. In this study, we investigate the connections between superlattice, AFM phase and superconductivity via the combined approaches of Te doping and application of external pressure. Our data reveal that the superconductivity of the ambient-pressure superconducting phase (SC-I) and the AFM long-ranged order as well as the superconductivity of the pressure-induced phase (SC-II) in the host samples can be synchronously tuned by Te doping. At x = 0.4, the SC-I and AFM long-range ordered phases as well as the SC-II phase disappear together, indicating that the two superconducting phases have intrinsic connections with the AFM phase. Furthermore, in-situ synchrotron x-ray diffraction measurements indicate that the superlattice structure in the x = 0.4 sample still exists at ambient pressure, but collapses at the same pressure where the superlattice of the superconducting samples is destructed. These results provide new insight into understanding the physics of this type of superconductors.

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The orbital characters of low-energy electronic structure in iron-chalcogenide superconductor K x Fe2−y Se2

Cited by 11 publications

References 32 publications

Anomalous correlation effects and unique phase diagram of electron-doped FeSe revealed by photoemission spectroscopy

Anomalous correlation effects and unique phase diagram of electron-doped FeSe revealed by photoemission spectroscopy

A unifying phase diagram with correlation-driven superconductor-to-insulator transition for the122☆series of iron chalcogenides

Superconductivity in pressurized Rb_0.8Fe_2−ySe_2−xTe_x

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The orbital characters of low-energy electronic structure in iron-chalcogenide superconductor K x Fe2−y Se2

Cited by 11 publications

References 32 publications

Anomalous correlation effects and unique phase diagram of electron-doped FeSe revealed by photoemission spectroscopy

Anomalous correlation effects and unique phase diagram of electron-doped FeSe revealed by photoemission spectroscopy

A unifying phase diagram with correlation-driven superconductor-to-insulator transition for the122☆series of iron chalcogenides

Superconductivity in pressurized Rb0.8Fe2−ySe2−xTex

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Superconductivity in pressurized Rb_0.8Fe_2−ySe_2−xTe_x