Observation of universal strong orbital-dependent correlation effects in iron chalcogenides

M Yi; Z-K Liu; Y Zhang; R Yu; J-X Zhu; J J Lee; R G Moore; F T Schmitt; W Li; S C Riggs; J-H Chu; B Lv; J Hu; M Hashimoto; S-K Mo; Z Hussain; Z Q Mao; C W Chu; I R Fisher; Q Si; Z-X Shen; D H Lu

doi:10.1038/ncomms8777

Observation of universal strong orbital-dependent correlation effects in iron chalcogenides

Nat Commun. 2015 Jul 23:6:7777. doi: 10.1038/ncomms8777.

Authors

M Yi¹, Z-K Liu¹, Y Zhang², R Yu³, J-X Zhu⁴, J J Lee¹, R G Moore⁵, F T Schmitt⁵, W Li⁵, S C Riggs¹, J-H Chu⁵, B Lv⁶, J Hu⁷, M Hashimoto⁸, S-K Mo⁹, Z Hussain⁹, Z Q Mao⁷, C W Chu⁶, I R Fisher¹, Q Si¹⁰, Z-X Shen¹, D H Lu⁸

Affiliations

¹ 1] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, California 94025, USA [2] Departments of Physics and Applied Physics, and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA.
² 1] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, California 94025, USA [2] Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, California 94720, USA.
³ 1] Department of Physics, Renmin University of China, Beijing 100872, China [2] Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA.
⁴ Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
⁵ Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, California 94025, USA.
⁶ Department of Physics, Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, USA.
⁷ Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA.
⁸ Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
⁹ Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, California 94720, USA.
¹⁰ Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA.

Abstract

Establishing the appropriate theoretical framework for unconventional superconductivity in the iron-based materials requires correct understanding of both the electron correlation strength and the role of Fermi surfaces. This fundamental issue becomes especially relevant with the discovery of the iron chalcogenide superconductors. Here, we use angle-resolved photoemission spectroscopy to measure three representative iron chalcogenides, FeTe0.56Se0.44, monolayer FeSe grown on SrTiO3 and K0.76Fe1.72Se2. We show that these superconductors are all strongly correlated, with an orbital-selective strong renormalization in the dxy bands despite having drastically different Fermi surface topologies. Furthermore, raising temperature brings all three compounds from a metallic state to a phase where the dxy orbital loses all spectral weight while other orbitals remain itinerant. These observations establish that iron chalcogenides display universal orbital-selective strong correlations that are insensitive to the Fermi surface topology, and are close to an orbital-selective Mott phase, hence placing strong constraints for theoretical understanding of iron-based superconductors.