A subtle balance between competing interactions in strongly correlated systems can be easily tipped by additional interfacial interactions in a heterostructure. This often induces exotic phases with unprecedented properties, as recently exemplified by high-Tc superconductivity in FeSe monolayer on the nonmagnetic SrTiO3. When the proximity-coupled layer is magnetically active, even richer phase diagrams are expected in iron-based superconductors (FeSCs), which however has not been explored due to the lack of a proper material system. One promising candidate is Sr2VO3FeAs, a naturally-assembled heterostructure of a FeSC and a Mott-insulating vanadium oxide. Here, using high-quality single crystals and high-accuracy 75As and 51V nuclear magnetic resonance (NMR) measurements, we show that a novel electronic phase is emerging in the FeAs layer below T0 ~ 155 K without either static magnetism or a crystal symmetry change, which has never been observed in other FeSCs. We find that frustration of the otherwise dominant Fe stripe and V Neel fluctuations via interfacial coupling induces a charge/orbital order with C4-symmetry in the FeAs layers, while suppressing the Neel antiferromagnetism in the SrVO3 layers. These findings demonstrate that the magnetic proximity coupling is effective to stabilize a hidden order in FeSCs and, more generally, in strongly correlated heterostructures.
@article{arxiv.1706.08157,
title = {Frustration-driven C4 symmetric orders in a hetero-structured iron-based superconductor},
author = {Jong Mok Ok and S. -H. Baek and C. Hoch and R. K. Kremer and S. Y. Park and Sungdae Ji and B. Buechner and J. -H. Park and S. I. Hyun and J. H. Shim and Yunkyu Bang and E. G. Moon and I. I. Mazin and Jun Sung Kim},
journal= {arXiv preprint arXiv:1706.08157},
year = {2017}
}