Prof. JunSung Kim [Pohang University of Science and Technology, South Korea]

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

Time: 10:00 - 11:00 AM, Tuesday, August 29, 2017

Place: Conference room 410, HPSTAR (Shanghai)

Host: Duckyoung Kim

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.

Biography of the Speaker:





- 2014 ~ Current : Associate professor in Physics Department, POSTECH

-2009 ~ 2013: Assistant professor in physics department, POSTECH

- 2006 ~ 2008: Staff scientist, Max-planck-Institute for solid state research, Stuttgart, Germany

[Selected Recent publications]

- Polymorphic Integration of Atomically thin metals and semiconductors by heteroepitaxy, Nature Nanotech. Accepted.

- Enhancement of superconductivity by interfacial phonons in perovskite-clad monolayers, PRL accepted

-20 K superconductivity in heavily electron doped surface layer of FeSe bulk crystal, Nature comm. 7 11116(2016)

-Anomalous magnetothermopower in a metallic frustrated antiferromagnet, PRL 116 087202 (2016)

- Charge ordering cascade with spin-orbit Mott dimer states in metallic iridium ditelluride, Nature comm. 6 7342 (2015).

- Superconductivity in FeSe: orbital-dirven nematicity sets the stage, Nature Mater. 14 210 (2015)

- Dimerization-induced Fermi surface reconstruction in IrTe2, PRL 113, 266406 (2014)

- Valley-polarized interlayer conduction of anisotropic Dirac fermions in SrMnBi2, PRL 113, 156602 (2014)