Band-selective gap opening by a <i>C</i> <sub>4</sub>-symmetric order in a proximity-coupled heterostructure Sr<sub>2</sub>VO<sub>3</sub>FeAs.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34789576.
- Also identified by DOI 10.1073/pnas.2105190118 and PMC identifier 8617490.
- Licence recorded as CC BY-NC-ND.
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Abstract
Complex electronic phases in strongly correlated electron systems are manifested by broken symmetries in the low-energy electronic states. Some mysterious phases, however, exhibit intriguing energy gap opening without an apparent signature of symmetry breaking (e.g., high-<i>T<sub>C</sub></i> cuprates and heavy fermion superconductors). Here, we report an unconventional gap opening in a heterostructured, iron-based superconductor Sr<sub>2</sub>VO<sub>3</sub>FeAs across a phase transition at <i>T</i> <sub>0</sub> ∼150 K. Using angle-resolved photoemission spectroscopy, we identify that a fully isotropic gap opens selectively on one of the Fermi surfaces with finite warping along the interlayer direction. This band selectivity is incompatible with conventional gap opening mechanisms associated with symmetry breaking. These findings, together with the unusual field-dependent magnetoresistance, suggest that the Kondo-type proximity coupling of itinerant Fe electrons to localized V spin plays a role in stabilizing the exotic phase, which may serve as a distinct precursor state for unconventional superconductivity.