Observation of Lattice and Andreev Bound States of Vortices in Ba0.6K0.4Fe2As2 Single Crystals with Scanning Tunneling Microscopy/Spectroscopy

Abstract

For a type-II superconductor, when the applied magnetic field is higher than the lower critical value Hc1, the magnetic flux will penetrate into the superconductor and form quantized vortices, which usually are arranged in an Abrikosov lattice. For the newly discovered iron pnictide superconductors, previous measurements have shown that, in electron-doped BaFe2As2, the vortices form a highly disordered structure. In addition, the density of states (DOS) within the vortex cores1 do not exhibit the Andreev bound states in conventional superconductors. In this Letter, we report the observation of a triangular vortex lattice and the Andreev bound states in hole-doped BaFe2As2 by using a low temperature scanning tunneling microscope (STM). Detailed study of the vortex cores reveals that the spectrum of the Andreev bound states inside the vortex core exhibits a distinct spatial evolution: at the center of the vortex core, it appears as a single peak at 0.5 mV below the Fermi-energy; away from the core center, it gradually evolves into two sub-peaks and they eventually fade out. The drastic differences between the vortex cores of the electron-doped and hole-doped counterparts are illusive to the pairing mechanism of the iron pnictide superconductors.

18 pages, 7 figures

References in corpus (15)

• Scanning tunneling spectroscopy of high-temperature superconductors
• Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
• Nearly Isotropic superconductivity in (Ba,K)Fe2As2
• Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$
• Momentum dependence of the superconducting gap in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Evolution of the electronic excitation spectrum with strongly diminishing hole-density in superconducting Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}
• Fully Gapped Superconducting State Based on a High Normal State Quasiparticle Density of States in Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ Single Crystals
• Low temperature specific heat of the hole-doped Ba_{0.6}K_{0.4}Fe_2As_2 single crystals and electron-doped SmFeAsO_{0.9}F_{0.1} samples
• Momentum-dependence of Superconducting Gap, strong-coupling dispersion Kink, and tightly bound Cooper pairs in the high-Tc (Sr,Ba)1-x(K,Na)xFe2As2 superconductors
• Evidence for Two Gaps and Breakdown of the Uemura Plot in Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ Single Crystals
• 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
• Vortex studies in superconducting Ba(Fe0.93Co0.07)2As2
• Angular resolved specific heat in iron-based superconductors: the case for nodeless extended $s$-wave gap
• Unveiling the Atomic and Electronic Structure at the Surface of the Parent Pnictide SrFe2As2
• Vortex core states in a minimal two-band model for iron-based superconductors

Cited by in corpus (32)

• Observation of a Robust Zero-energy Bound State in Iron-based Superconductor Fe(Te,Se)
• Scanning Tunneling Microscopy/Spectroscopy of Vortices in LiFeAs
• Crossover from weak to strong pairing in unconventional superconductors
• Nanoscale assembly of superconducting vortices with scanning tunnelling microscope tip
• Evidence of a spin resonance mode in the iron-based superconductor Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ from scanning tunneling spectroscopy
• Observation of magnetic adatom-induced Majorana vortex and its hybridization with field-induced Majorana vortex in an iron-based superconductor
• A comprehensive scenario of the single crystal growth and doping dependence of resistivity and anisotropic upper critical fields in (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$ ($0.22\le x\le 1$)
• Lower critical field and SNS-Andreev spectroscopy of 122-arsenides: Evidence of nodeless superconducting gap
• Anisotropic Superconducting Gap and Elongated Vortices with Caroli-De-Gennes-Matricon States in the New Superconductor Ta4Pd3Te16
• Friedel Oscillations of Vortex Bound States Under Extreme Quantum Limit in KCa2Fe4As4F2
• Unexpected weak spatial variation of local density of sates induced by individual Co impurity atoms in Na(Fe{1-x}Cox)As as revealed by scanning tunneling spectroscopy
• Coexistence of ferromagnetism and superconductivity in iron based pnictides: a time resolved magnetooptical study
• Superconductivity in Undoped BaFe2As2 by Tetrahedral Geometry Design
• Emergent vortex Majorana zero mode in iron-based superconductors
• On the Structure of Superconducting Order Parameter in High-Temperature Fe-Based Superconductors
• Vortex creep and critical current densities in superconducting (Ba,K)Fe${}_2$As${}_2$ single crystals
• Strong-coupling superconductivity and weak vortex pinning in Ta-doped CsV${}_3$Sb${}_5$ single crystals
• Colossal band renormalization and stoner ferromagnetism induced by electron-antiferromagnetic-magnon coupling
• Domain Walls in Normal and Superconducting States of Iron Pnictides
• Electron-boson-interaction induced particle-hole symmetry breaking of conductance into subgap states in superconductors
• SANS Study of Vortex Lattice Structural Transition in Optimally Doped (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$
• Study of antiferromagnetic and nematic phase transitions in $BaF{e}_2(A{s}_{1-x}{P}_x{)}_2$ by AC micro-calorimetry and SQUID magnetometry
• Direct Observation of the Scale Relation between Density of States and Pairing Gap in a Dirty Superconductor
• Planar pinning induced, lowering of vortex dimensionality and low field melting in a single crystal of Ba0.6K0.4Fe2As2
• Absence of hexagonal to square structural transition in LiFeAs vortex matter
• Giant Thermoelectric Response of Fluxons in Superconductors
• Distinct Properties of Vortex Bound States Driven by Temperature
• Tuning Bound States of Symmetry-Breaking Vortices via Unidirectional Charge Density Wave in a Transition-Metal Dichalcogenide Superconductor
• Helical Topological Superconducting Pairing at Finite Excitation Energies
• Vanishing vortex creep at the transition from ordered to disordered vortex phases in Ba${}_{0.64}$K${}_{0.36}$Fe${}_2$As${}_2$
• Quantum interference among vortex bound states in superconductors
• Zero Energy Bound States on Nano Atomic Line Defect in Iron-based High Temperature Superconductors