Role of the 245 phase in alkaline iron selenide superconductors revealed by high-pressure studies

Gao, Peiwen; Yu, Rong; Sun, Liling; Wang, Hangdong; Wang, Zhen; Wu, Qi; Fang, Minghu; Chen, Genfu; Guo, Jing; Zhang, Chao; Gu, Dachun; Tian, Huanfang; Li, Jianqi; Liu, Jing; Li, Yanchun; Li, Xiaodong; Jiang, Sheng; Yang, Ke; Li, Aiguo; Si, Qimiao; Zhao, Zhongxian

doi:10.1103/physrevb.89.094514

Cited by 35 publications

(47 citation statements)

References 49 publications

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“…The commonly observed 245 phase exists in all the nominal compositions of Rb 0.8 Fe 2 Se 2−z S z as a mesoscopically separated phase. Note that the Fe content is in fact less than 2 which means that all of the samples are in the two phase coexistence region [11][12][13][14][15][16][17][18][19][20][21][22][23] .…”

Section: Rb08fe2s2mentioning

confidence: 99%

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Elucidating the magnetic and superconducting phases in the alkali metal intercalated iron chalcogenides

Wang

Bourret-Courchesne

et al. 2016

Phys. Rev. B

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The complex interdigitated phases have greatly frustrated attempts to document the basic features of the superconductivity in the alkali metal intercalated iron chalcogenides. Here, using elastic neutron scattering, energy-dispersive x-ray spectroscopy, and resistivity measurements, we elucidate the relations of these phases in RbxFeySe2−zSz. We find: i) the iron content is crucial in stabilizing the stripe antiferromagnetic (AF) phase with rhombic iron vacancy order (y ≈ 1.5), the block AF phase with √ 5 × √ 5 iron vacancy order (y ≈ 1.6), and the iron vacancy-free phase (y ≈ 2); ii) the iron vacancy-free superconducting phase (z = 0) evolves into an iron vacancy-free metallic phase with sulfur substitution (z > 1.5) due to the progressive decrease of the electronic correlation strength. Both the stripe AF phase and the block AF phase are Mott insulators. The iron-rich compounds (y > 1.6) undergo a first order transition from an iron vacancy disordered phase at high temperatures into the √ 5 × √ 5 iron vacancy ordered phase and the iron vacancy-free phase below Ts. Our data demonstrate that there are miscibility gaps between these three phases. The existence of the miscibility gaps in the iron content is a key to understanding the relationship between these complicated phases.

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Section: Rb08fe2s2mentioning

confidence: 99%

“…1 (x ≈ 0.8, y ≈ 1.6, referred to as the 245 phase) always seems to be mesoscopically interdigitated with the SC phase that has been suggested to be an iron vacancy free phase in the studies to-date [10][11][12][13][14][15][16][17][18][19][20][21][22][23] . The relationships between the two phases are still under debate.…”

Section: Introductionmentioning

confidence: 99%

Elucidating the magnetic and superconducting phases in the alkali metal intercalated iron chalcogenides

Wang

Bourret-Courchesne

et al. 2016

Phys. Rev. B

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“…This phase has been observed around 100-300 K in the multi-band metallic phase by angle resolved photoemission spectroscopy (ARPES) [26]. In addition, a recent high pressure study [27] has underlined the importance of the OSMP phase as an intermediate phase between the iron-vacancy ordered insulating texture and the minority metallic phase. Also a recent high energy x-ray emission (XES) study has found anomalous evolution of the magnetic phase below 300 K that can arXiv:1501.06745v1 [cond-mat.supr-con] 27 Jan 2015 be assigned to the OSMP phase [28].…”

Section: Introductionmentioning

confidence: 96%

Direct observation of nanoscale interface phase in the superconducting chalcogenideKxFe2−ySe2with intrinsic phase separation

et al. 2015

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We have used scanning micro x-ray diffraction to characterize different phases in superconducting KxFe2−ySe2 as a function of temperature, unveiling the thermal evolution across the superconducting transition temperature (Tc ∼32 K), phase separation temperature (Tps ∼520 K) and iron-vacancy order temperature (Tvo ∼580 K). In addition to the iron-vacancy ordered tetragonal magnetic phase and orthorhombic metallic minority filamentary phase, we have found a clear evidence of the interface phase with tetragonal symmetry. The metallic phase is surrounded by this interface phase below ∼300 K, and is embedded in the insulating texture. The spatial distribution of coexisting phases as a function of temperature provides a clear evidence of the formation of protected metallic percolative paths in the majority texture with large magnetic moment, required for the electronic coherence for the superconductivity. Furthermore, a clear reorganization of iron-vacancy order around the Tps and Tc is found with the interface phase being mostly associated with a different iron-vacancy configuration, that may be important for protecting the percolative superconductivity in KxFe2−ySe2.

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“…The OSMP phase arises in multiorbital Hubbard models of the FeSCs, which contain both Hubbard interactions and Hund's coupling 11,12 . Evidence for the OSMP has also come from a variety of other measurements [13][14][15][16] . A complementary approach to the electron correlations of the FeSCs describes the localization-delocalization phenomena in the form of an orbital differentiation and a coherence-incoherence crossover 17,18 , though OSMP is not explicitly invoked.…”

Section: Introductionmentioning

confidence: 99%

Orbital-selective Mott phase in multiorbital models for iron pnictides and chalcogenides

2017

Phys. Rev. B

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There is increasing recognition that the multiorbital nature of the 3d electrons is important to the proper description of the electronic states in the normal state of the iron-based superconductors. Earlier studies of the pertinent multiorbital Hubbard models identified an orbital-selective Mott phase, which anchors the orbitalselective behavior seen in the overall phase diagram. An important characteristics of the models is that the orbitals are kinetically coupled -i.e. hybridized -to each other, which makes the orbital-selective Mott phase especially nontrivial. A U (1) slave-spin method was used to analyze the model with nonzero orbital-level splittings. Here we develop a Landau free-energy functional to shed further light on this issue. We put the microscopic analysis from the U (1) slave-spin approach in this perspective, and show that the intersite spin correlations are crucial to the renormalization of the bare hybridization amplitude towards zero and the concomitant realization of the orbital-selective Mott transition. Based on this insight, we discuss additional ways to study the orbital-selective Mott physics from a dynamical competition between the interorbital hybridization and collective spin correlations. Our results demonstrate the robustness of the orbital-selective Mott phase in the multiorbital models appropriate for the iron-based superconductors.

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Role of the 245 phase in alkaline iron selenide superconductors revealed by high-pressure studies

Cited by 35 publications

References 49 publications

Elucidating the magnetic and superconducting phases in the alkali metal intercalated iron chalcogenides

Elucidating the magnetic and superconducting phases in the alkali metal intercalated iron chalcogenides

Direct observation of nanoscale interface phase in the superconducting chalcogenideKxFe2−ySe2with intrinsic phase separation

Orbital-selective Mott phase in multiorbital models for iron pnictides and chalcogenides

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