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Research Article | Open Access

Visualization of the electronic phase separation in superconducting KxFe2−ySe2

Yujie Chen1, Juan Jiang2,3, Haifeng Yang4, Pavel Dudin5, Alexey Barinov6, Zhongkai Liu4,7, Haihu Wen8, Lexian Yang1,9( ), Yulin Chen1,2,4,7( )
State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai 201210, China
Synchrotron SOLEIL, L’Orme des Merisiers, Saint Aubin-BP 48, 91192 Gif sur Yvette Cedex, France
Elettra-Sincrotrone Trieste, Trieste, Basovizza 34149, Italy
ShanghaiTech Laboratory for Topological Physics, Shanghai 200031, China
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
Frontier Science Center for Quantum Information, Beijing 100084, China
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Graphical Abstract

Abstract

Type-II iron-based superconductors (Fe-SCs), the alkali-metal-intercalated iron selenide AxFe2−ySe2 (A = K, Tl, Rb, etc.) with a superconducting transition temperature of 32 K, exhibit unique properties such as high Néel temperature, Fe-vacancies ordering, antiferromagnetically ordered insulating state in the phase diagram, and mesoscopic phase separation in the superconducting materials. In particular, the electronic and structural phase separation in these systems has attracted intensive attention since it provides a platform to unveil the insulating parent phase of type-II Fe-SCs that mimics the Mott parent phase in cuprates. In this work, we use spatial- and angle-resolved photoemission spectroscopy to study the electronic structure of superconducting KxFe2−ySe2. We observe clear electronic phase separation of KxFe2−ySe2 into metallic islands and insulating matrix, showing different K and Fe concentrations. While the metallic islands show strongly dispersive bands near the Fermi level, the insulating phase shows an energy gap up to 700 meV and a nearly flat band around 700 meV below the Fermi energy, consistent with previous experimental and theoretical results on the superconducting K1−xFe2Se2 (122 phase) and Fe-vacancy ordered K0.8Fe1.6Se2 (245 phase), respectively. Our results not only provide important insights into the mysterious composition of phase-separated superconducting and insulating phases of KxFe2−ySe2, but also present their intrinsic electronic structures, which will shed light on the comprehension of the unique physics in type-II Fe-SCs.

Keywords

spatial- and angle-resolved photoemission spectroscopy (μ-ARPES)iron-based superconductorsphase separationelectronic structure

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Nano Research
Volume 14 Issue 3,
March 2021
Pages 823-828
DOI: 10.1007/s12274-020-3119-8
Cite this article:
Chen Y, Jiang J, Yang H, et al. Visualization of the electronic phase separation in superconducting KxFe2−ySe2. Nano Research, 2021, 14(3): 823-828. https://doi.org/10.1007/s12274-020-3119-8
Topics:
Copper compoundsElectronic structureIronIron compoundsPhotoelectron spectroscopySelenium compounds

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Received: 04 July 2020
Revised: 03 September 2020
Accepted: 15 September 2020
Published: 01 March 2021
© The Author(s) 2020

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