Surface terminations and layer-resolved spectroscopy in 122 iron pnictide superconductors

Abstract

The surface terminations of 122-type alkaline earth metal iron pnictides AEFe2As2 (AE = Ca, Ba) are investigated with scanning tunneling microscopy/spectroscopy (STM/STS). Cleaving these crystals at a cryogenic temperature yields a large majority of terminations with atomically resolved square-root-two (rt2) or 1*2 lattice, as well as the very rare terminations with 1*1 symmetry. By means of lattice alignment and chemical marking, we identify these terminations as rt2-AE, 1*2-As, and rt2-Fe surfaces, respectively. Layer-resolved spectroscopy on these terminating surfaces reveals a well-defined superconducting gap on the As terminations, while the gap features become weaker and absent on AE and Fe terminations respectively. The local gap features are hardly affected by the surface reconstruction on As or AE surface, whereas a suppression of them along with the in-gap states can be induced by As vacancies. The emergence of two impurity resonance peaks at +-2 meV is consistent with the sign-reversal pairing symmetry. The definite identification of surface terminations and their spectroscopic signatures shall provide a more comprehensive understanding of the high-temperature superconductivity in multilayered iron pnictides.

References in corpus (27)

• The Puzzle of High Temperature Superconductivity in Layered Iron Pnictides and Chalcogenides
• Superconductivity in Iron Compounds
• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• Spin density wave anomaly at 140 K in the ternary iron arsenide BaFe2As2
• Kinetic frustration and the nature of the magnetic and paramagnetic states in iron pnictides and iron chalcogenides
• Effects of Co substitution on thermodynamic and transport properties and anisotropic $H_{c2}$ in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ single crystals
• Giant and anisotropic many-body spin-orbit tunability in a strongly correlated kagome magnet
• Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$
• Observation of a Robust Zero-energy Bound State in Iron-based Superconductor Fe(Te,Se)
• Spectroscopic scanning tunneling microscopy insights into Fe-based superconductors
• Observation of Lattice and Andreev Bound States of Vortices in Ba0.6K0.4Fe2As2 Single Crystals with Scanning Tunneling Microscopy/Spectroscopy
• The Unusual Superconducting State at 49 K in Electron-Doped CaFe2As2 at Ambient
• Stabilization of an ambient pressure, collapsed tetragonal phase in CaFe2As2 and tuning of the orthorhombic / antiferromagnetic transition temperature by over 70 K by control of nano-precipitates
• The cleavage surface of the BaFe_(2-x)Co_(x)As_(2) and Fe_(y)Se_(1-x)Te_(x) superconductors: from diversity to simplicity
• Nanoscale superconducting gap variations, strong coupling signatures and lack of phase separation in optimally doped BaFe1.86Co0.14As2
• Surface Geometric and Electronic Structure of BaFe2As2(001)
• Close relationship between superconductivity and the bosonic mode in Ba0.6K0.4Fe2As2 and Na(Fe0.975Co0.025)As
• Measurement of a Sign-Changing Two-Gap Superconducting Phase in Electron-Doped Ba(Fe_{1-x}Co_x)_2As_2 Single Crystals using Scanning Tunneling Spectroscopy
• Electronic structure of oxygen-free 38K superconductor Ba1-xKxFe2As2 in comparison with BaFe2As2 from first principles
• Dopant Clustering, Electronic Inhomogeneity, and Vortex Pinning in Iron-Based Superconductors
• Atomic and electronic structures of ternary iron arsenides $A$Fe${}_2$As${}_2$(001) surfaces ($A$=Ba, Sr, or Ca)
• Universal $\sqrt{2}\times \sqrt{2}$ structure and short-range charge order at the surfaces of BaFe${}_{2-x}$Co${}_x$As${}_2$ compounds with various Co doping levels
• Nanoscale Surface Element Identification and Dopant Homogeneity in the High-$T_c$ Superconductor Pr${}_x$Ca${}_{1-x}$Fe${}_2$As${}_2$
• Unconventional pairing originating from disconnected Fermi surfaces in the iron-based superconductor
• BaFe2As2 Surface Domains and Domain Walls: Mirroring the Bulk Spin Structure
• Experimental investigation of the electronic structure of Ca${}_{0.83}$La${}_{0.17}$Fe${}_2$As${}_2$
• Surface adatom conductance filtering in scanning tunneling spectroscopy of Co-doped BaFe2As2 iron pnictide superconductors

Cited by in corpus (14)

• Electronic nature of chiral charge order in the kagome superconductor CsV3Sb5
• Intrinsic nature of chiral charge order in the kagome superconductor RbV3Sb5
• Spin-orbit quantum impurity and quantization in a topological magnet
• Effect of surface morphology and magnetic impurities on the electronic structure in cobalt-doped BaFe2As2 superconductors
• Orbital selectivity of layer resolved tunneling on iron superconductor Ba0.6K0.4Fe2As2
• Competition of spatially inhomogeneous states in antiferromagnetic Hubbard model
• Low work function in the 122-family of iron-based superconductors
• Perspective: imaging atomic step geometry to determine surface terminations of kagome materials and beyond
• Genuine Electronic Structure and Superconducting Gap Structure in (Ba${}_{0.6}$K${}_{0.4}$)Fe${}_2$As${}_2$ Superconductor
• Common ($\pi$,$\pi$) Band Folding and Surface Reconstruction in FeAs-Based Superconductors
• Revealing the intrinsic superconducting gap anisotropy in surface-neutralized BaFe${}_2$(As${}_{0.7}$P${}_{0.3}$)${}_2$
• Surface reconstruction and charge modulation in BaFe2As2 superconducting film
• Enhanced Surface Superconductivity in Ba(Fe${}_{0.95}$Co${}_{0.05}$)${}_2$As${}_2$
• Spin-orbit quantum impurity in a topological kagome magnet