Jong Mok Ok
Pohang University of Science and Technology
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Jong Mok Ok.
Physical Review Letters | 2017
Seokhwan Choi; S. Johnston; Won-Jun Jang; Klaus Koepernik; Ken Nakatsukasa; Jong Mok Ok; Hyun-Jung Lee; Hyun Woo Choi; Alex Taekyung Lee; Alireza Akbari; Yannis K. Semertzidis; Yunkyu Bang; Jun Sung Kim; Jhinhwan Lee
Interfacial phonons between iron-based superconductors (FeSCs) and perovskite substrates have received considerable attention due to the possibility of enhancing preexisting superconductivity. Using scanning tunneling spectroscopy, we studied the correlation between superconductivity and e-ph interaction with interfacial phonons in an iron-based superconductor Sr_{2}VO_{3}FeAs (T_{c}≈33 K) made of alternating FeSC and oxide layers. The quasiparticle interference measurement over regions with systematically different average superconducting gaps due to the e-ph coupling locally modulated by O vacancies in the VO_{2} layer, and supporting self-consistent momentum-dependent Eliashberg calculations provide a unique real-space evidence of the forward-scattering interfacial phonon contribution to the total superconducting pairing.
Physical Review Letters | 2017
Seokhwan Choi; Hyoung Joon Choi; Jong Mok Ok; Yeonghoon Lee; Won Jun Jang; Alex Taekyung Lee; Young Kuk; SungBin Lee; Andreas J. Heinrich; Sang-Wook Cheong; Yunkyu Bang; S. Johnston; Jun Sung Kim; Jhinhwan Lee
We explore a new mechanism for switching magnetism and superconductivity in a magnetically frustrated iron-based superconductor using spin-polarized scanning tunneling microscopy (SPSTM). Our SPSTM study on single-crystal Sr_{2}VO_{3}FeAs shows that a spin-polarized tunneling current can switch the Fe-layer magnetism into a nontrivial C_{4} (2×2) order, which cannot be achieved by thermal excitation with an unpolarized current. Our tunneling spectroscopy study shows that the induced C_{4} (2×2) order has characteristics of plaquette antiferromagnetic order in the Fe layer and strongly suppresses superconductivity. Also, thermal agitation beyond the bulk Fe spin ordering temperature erases the C_{4} state. These results suggest a new possibility of switching local superconductivity by changing the symmetry of magnetic order with spin-polarized and unpolarized tunneling currents in iron-based superconductors.
Nature Communications | 2017
Jong Mok Ok; S.-H. Baek; C. Hoch; R. K. Kremer; Soo-Jin Park; Sungdae Ji; B. Büchner; Joonbum Park; S. I. Hyun; Je-Ho Shim; Yunkyu Bang; E. G. Moon; I. I. Mazin; Jun Sung Kim
A subtle balance between competing interactions in iron-based superconductors (FeSCs) can be tipped by additional interfacial interactions in a heterostructure, often inducing exotic phases with unprecedented properties. Particularly when the proximity-coupled layer is magnetically active, rich phase diagrams are expected in FeSCs, but this has not been explored yet. Here, using high-accuracy 75As and 51V nuclear magnetic resonance measurements, we investigate an electronic phase that emerges in the FeAs layer below T0 ~ 155 K of Sr2VO3FeAs, a naturally assembled heterostructure of an FeSC and a Mott-insulating vanadium oxide. We find that frustration of the otherwise dominant Fe stripe and V Neel fluctuations via interfacial coupling induces a charge/orbital order in the FeAs layers, without either static magnetism or broken C4 symmetry, while suppressing the Neel antiferromagnetism in the SrVO3 layers. These findings demonstrate that the magnetic proximity coupling stabilizes a hidden order in FeSCs, which may also apply to other strongly correlated heterostructures.Iron-based superconductors exhibit complex couplings between different electronic degrees of freedom, leading to unusual correlated phases. Ok et al. show that Sr2VO3FeAs develops a hidden order state due to frustrated interactions between the magnetic fluctuations of its SrVO3 and SrFeAs layers.
arXiv: Superconductivity | 2016
Seokhwan Choi; Won-Jun Jang; Jong Mok Ok; Hyun Woo Choi; Hyunjung Lee; Se-Jong Kahng; Young Kuk; Ja-Yong Koo; SungBin Lee; Sang-Wook Cheong; Yunkyu Bang; Jun Sung Kim; Jhinhwan Lee
Physical Review Letters | 2016
Stevan Arsenijević; Jong Mok Ok; Peter Robinson; Saman Ghannadzadeh; M. I. Katsnelson; Jun Sung Kim; Nigel E. Hussey
Bulletin of the American Physical Society | 2017
Jhinhwan Lee; Seokhwan Choi; Won-Jun Jang; Yannis K. Semertzidis; Jong Mok Ok; Hyunjung Lee; Alireza Akbari; Jun-Sung Kim; Alex Taekyung Lee; Ken Nakatsukasa; S. Johnston; Yunkyu Bang
Bulletin of the American Physical Society | 2017
Seokhwan Choi; Won-Jun Jang; Jong Mok Ok; Hyunjung Lee; Se-Jong Kahng; Young Kuk; Ja-Yong Koo; SungBin Lee; Sang-Wook Cheong; Yunkyu Bang; Jun Sung Kim; Jhinhwan Lee
arXiv: Superconductivity | 2016
Seokhwan Choi; Won-Jun Jang; Jong Mok Ok; Hyun Woo Choi; Hyun-Jung Lee; Se-Jong Kahng; Young Kuk; Ja-Yong Koo; SungBin Lee; Sang-Wook Cheong; Yunkyu Bang; Jun Sung Kim; Jhinhwan Lee
Bulletin of the American Physical Society | 2016
Jhinhwan Lee; Seokhwan Choi; Hyunjung Lee; Won-Jun Jang; Jong Mok Ok; Hyun Woo Choi; Jin Oh Jung; Dong Hyun Son; Hwan Soo Suh; Yannis K. Semertzidis; Jun Sung Kim
Bulletin of the American Physical Society | 2016
Won-Jun Jang; Seokhwan Choi; Jong Mok Ok; Hyun Woo Choi; Hyunjung Lee; Jin Oh Jung; Dong Hyun Son; Hwan Soo Suh; Jun Sung Kim; Yannis K. Semertzidis; Jhinhwan Lee