Defect states in LiFeAs as seen by low temperature scanning tunneling microscopy and spectroscopy

Abstract

We present a microscopic investigation of frequently observed impurity-induced states in stoichiometric LiFeAs using low temperature scanning tunneling microscopy and spectroscopy (STM/STS). Our data reveal seven distinct well defined defects which are discernible in topographic measurements. Depending on their local topographic symmetry, we are able to assign five defect types to specific lattice sites at the Li, Fe and As positions. The most prominent result is that two different defect types have a remarkably different impact on the superconducting state. A specific and quite abundant Fe-defect with $D_2$-symmetry generates significant impurity-induced additional states primarily at positive bias voltage with pronounced peaks in the on-site local density of states (LDOS) at about 4~mV and 12~mV. On the other hand, a $D_4$-symmetric As-defect causes a significantly enhanced LDOS at both positive and negative bias voltages. We expect that these findings provide fresh input for further experimental and theoretical studies on elucidating the nature of superconductivity in LiFeAs.

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Cited by in corpus (5)

• Tunable vortex Majorana zero modes in LiFeAs superconductor
• Imaging the Real Space Structure of the Spin Fluctuations in an Iron-based superconductor
• An ultra-high vacuum scanning tunneling microscope operating at sub-Kelvin temperatures and high magnetic fields for spin-resolved measurements
• Spectroscopic evidence of nematic fluctuations in LiFeAs
• Absence of hexagonal to square structural transition in LiFeAs vortex matter