1. Nematic electronic structure in the 'parent' state of the iron-based superconductor Ca[([Fe.sub.1-x][Co.sub.x]).sub.2][As.sub.2]
- Author
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Chuang, T.-M., Allan, M.P., Lee, Jinho, Xie, Yang, Ni, Ni, Bud'ko, S.L., Boebinger, G.S., Canfield, P.C., and Davis, J.C.
- Subjects
High temperature superconductors -- Chemical properties ,High temperature superconductors -- Electric properties ,High temperature superconductors -- Research ,Cobalt -- Chemical properties ,Cobalt -- Structure ,Cobalt -- Research ,Science and technology - Abstract
The mechanism of high-temperature superconductivity in the newly discovered iron-based superconductors is unresolved. We use spectroscopic imaging--scanning tunneling microscopy to study the electronic structure of a representative compound Ca[Fe.sub.1.94][Co.sub.0.06][As.sub.2] in the 'parent' state from which this superconductivity emerges. Static, unidirectional electronic nanostructures of dimension eight times the inter--iron-atom distance [a.sub.Fe-Fe] and aligned along the crystal a axis are observed. In contrast, the delocalized electronic states detectable by quasiparticle interference imaging are dispersive along the b axis only and are consistent with a nematic [[alpha].sub.2] band with an apparent band folding having wave vector [??] [congruent] [+ or -]2[pi]/[8a.sub.Fe-Fe] along the a axis. All these effects rotate through 90 degrees at orthorhombic twin boundaries, indicating that they are bulk properties. As none of these phenomena are expected merely due to crystal symmetry, underdoped ferropnictides may exhibit a more complex electronic nematic state than originally expected. 10.1126/science.1181083
- Published
- 2010
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