Frustration-driven C4 symmetric orders in a hetero-structured iron-based superconductor

TL;DR

This study reveals a novel C4-symmetric charge/orbital order in a heterostructured iron-based superconductor induced by interfacial magnetic coupling, without static magnetism or symmetry change, highlighting the role of frustration in stabilizing hidden orders.

Contribution

It demonstrates that magnetic proximity coupling in a heterostructure can induce a new electronic phase with C4 symmetry in iron-based superconductors, a phenomenon not previously observed.

Findings

Emergence of a charge/orbital order below 155 K without static magnetism.

Suppression of Neel antiferromagnetism in SrVO3 layers.

Interfacial coupling induces frustration-driven C4 symmetry in FeAs layers.

Abstract

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.