Abstract
Motivated by recent experimental reports of significant spin–orbit coupling (SOC) and a sign-changing order-parameter in the Li1−xFex(OHFe)1−yZnySe superconductor with only electron pockets present, we study the possible Cooper-pairing symmetries and their quasiparticle interference (QPI) signatures. We find that each of the resulting states—s-wave, d-wave and helical p-wave—can have a fully gapped density of states consistent with angle-resolved photoemission spectroscopy experiments and, due to SOC, are a mixture of spin singlet and triplet components leading to intra- and inter-band features in the QPI signal. Analyzing predicted QPI patterns we find that only the spin-triplet dominated even parity A1g (s-wave) and B2g (d-wave) pairing states are consistent with the experimental data. Additionally, we show that these states can indeed be realized in a microscopic model with atomic-like interactions and study their possible signatures in spin-resolved STM experiments.
Highlights
In iron-based superconductors, it has been widely believed that superconductivity is driven by repulsive interactions, enhanced by the presence of the spin fluctuations associated with the parent antiferromagnetic state
We remind the reader that the highly electron-doped Fe-chalcogenides, in particular the (Li1−xFex)OHFeSe system, have been discussed intensively in the context of the standard model of spinfluctuation induced spin singlet pairing in the limit of weak spin–orbit coupling (SOC)
For nonzero SOC, the superconducting order parameter is a combination of spin singlet and spin triplet gaps in each state
Summary
Pockets present, we study the possible Cooper-pairing symmetries and their quasiparticle interference (QPI) signatures. We find that each of the resulting states—s-wave, d-wave and helical p-wave—can have a fully gapped density of states consistent with angle-resolved photoemission spectroscopy experiments and, due to SOC, are a mixture of spin singlet and triplet components leading to intraand inter-band features in the QPI signal. Analyzing predicted QPI patterns we find that only the spintriplet dominated even parity A1g (s-wave) and B2g (d-wave) pairing states are consistent with the experimental data. We show that these states can be realized in a microscopic model with atomic-like interactions and study their possible signatures in spin-resolved STM experiments
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