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Featured researches published by Wonsig Jung.


Physical Review B | 2011

Warping effects in the band and angular-momentum structures of the topological insulator Bi2Te3

Wonsig Jung; Y. K. Kim; Beomyoung Kim; Yoonyoung Koh; Chul Koo Kim; Masaharu Matsunami; Shin-ichi Kimura; Masashi Arita; Kenya Shimada; Jung Hoon Han; Ju-Young Kim; B. K. Cho; Changyoung Kim

We performed angle resolved photoemission (ARPES) experiments on Bi2Te3 with circularly polarized light. ARPES data show very strong circular dichroism, indicating existence of orbital angular momentum (OAM). Moreover, the alignment of OAM is found to have a strong binding energy dependence. Such energy dependence comes from a relatively strong band warping effect in Bi2Te3 compared to Bi2Se3. OAM close to Dirac point has an ideal chiral structure (sin ?) without out-of-plane component. Warping effect comes in as the binding energy decreases and circular dichroism along a constant energy contour can no longer be explained by a simple sin? function but requires a sin3? term. When the warping effect becomes even stronger near the Fermi energy, circular dichroism gains an additional sin6? term. Such behavior is found to be compatible with the theoretically predicted OAM structure.


Physical Review B | 2012

Spin and orbital angular momentum structure of Cu(111) and Au(111) surface states

Beomyoung Kim; C. Kim; Panjin Kim; Wonsig Jung; Y. K. Kim; Yoonyoung Koh; Masashi Arita; Kenya Shimada; Hirofumi Namatame; M. Taniguchi; Jaejun Yu; Changyoung Kim

We performed angle resolved photoemission (ARPES) studies on Cu(111) and Au(111) surface states with circularly polarized light. Existence of local orbital angular momentum (OAM) is confirmed as has been predicted to be broadly present in a system with an inversion symmetry breaking (ISB). The single band of Cu(111) surface states is found to have chiral OAM in spite of very small spin-orbit coupling (SOC) in Cu, which is consistent with theoretical prediction. As for Au(111), we observe split bands for which OAM for the inner and outer bands are parallel, unlike the Bi2Se3 case. We also performed first principles calculation and the results are found to be consistent with the experimental results. Moreover, majority of OAM is found to be from d-orbitals and a small contribution has p-orbital origin which is anti-aligned to the spins. We derive an effective Hamiltonian that incorporates the role of OAM and used it to extract the OAM and spin structures of surface states with various SOC strength. We discuss the evolution of angular momentum structures from pure OAM case to a strongly spin-orbit entangled state. We predict that the transition occurs through reversal of OAM direction at a k-point in the inner band if the system has a proper SOC strength.


International Journal of Sports Medicine | 2012

Immunological Impact of Taekwondo Competitions

Yong Won Lee; Shin Kw; Paik Iy; Wonsig Jung; Seung Yun Cho; Sang Tae Choi; Kim Hd; Jaesang Kim

Immunological changes in elite adolescent female athletes during Taekwondo competitions were investigated on-field. 6 female athletes (16.7 ± 0.8 year-old) volunteered and performed 5 bouts of demonstration Taekwondo competitions simulating real tournaments in intensity, duration, and break-time intervals on the same day. Blood samples were taken before, after the competitions and during the recovery, respectively. Immunological changes and oxidative stress in peripheral blood mononuclear cells were evaluated by flow-cytometry. During the competitions, exercise intensity was 92.2 ± 3.8% (86.1~95.7) of the maximal heart rate. Blood lactate increased immediately after the competitions (p=0.0165) and decreased to baseline during recovery. Intracellular reactive oxygen species (ROS) in the peripheral blood increased continuously during recovery (p<0.05, respectively). Natural killer cells increased immediately after the competitions (p=0.0006), and decreased during recovery. B and T cells increased immediately after the competitions and remained elevated throughout recovery (p<0.05, respectively). CD4/CD8 ratio after the competitions was decreased (p=0.0091) and returned to baseline during recovery. These results suggest that the immunological function of the elite female adolescent athletes could be attenuated after Taekwondo competitions. Further large-scaled Taekwondo studies on immunologic and apoptotic changes related to oxidative stress should be performed for improving and protecting the health of adolescent athletes.


Physical Review B | 2013

Microscopic mechanism for asymmetric charge distribution in Rashba-type surface states and the origin of the energy splitting scale

Beomyoung Kim; Panjin Kim; Wonsig Jung; Y. K. Kim; Yoonyoung Koh; Wonshik Kyung; Joonbum Park; M. Matsunami; Shin-ichi Kimura; Jun Sung Kim; Jung Hoon Han; Changyoung Kim

Microscopic mechanism for the Rashba-type band splitting is examined in detail. We show how asymmetric charge distribution is formed when local orbital angular momentum (OAM) and crystal momentum get interlocked due to surface effects. An electrostatic energy term in the Hamiltonian appears when such OAM and crystal momentum dependent asymmetric charge distribution is placed in an electric ?eld produced from an inversion symmetry breaking (ISB). Analysis by using an effective Hamiltonian shows that, as the atomic spin-orbit coupling (SOC) strength increases from weak to strong, originally OAM-quenched states evolve into well-de?ned chiral OAM states and then to total angular momentum J-states. In addition, the energy scale of the band splitting changes from atomic SOC energy to electrostatic energy. To con?rm the validity of the model, we study OAM and spin structures of Au(111) system by using an effective Hamiltonian for the d-orbitals case. As for strong SOC regime, we choose Bi2Te2Se as a prototype system. We performed circular dichroism angle resolved photoemission spectroscopy experiments as well as ?rst-principles calculations. We ?nd that the effective model can explain various aspects of spin and OAM structures of the system.


Physical Review B | 2011

Electronic Structure of Detwinned BaFe(2) As(2) from Photoemission and First Principles

Y. K. Kim; Hyungju Oh; Chul Koo Kim; Dongjoon Song; Wonsig Jung; Beomyoung Kim; Hyoung Joon Choi; Changyoung Kim; Bumsung Lee; Seunghyun Khim; Hyung-Joon Kim; Kee-Hoon Kim; Jongbeom Hong; Y.S. Kwon


Physical Review B | 2012

Oxygen-content-dependent electronic structures of electron-doped cuprates

Dongjoon Song; Seung Ryong Park; Chul Koo Kim; Y. K. Kim; C. S. Leem; Sungkyun Choi; Wonsig Jung; Yoonyoung Koh; Garam Han; Yoshiyuki Yoshida; H. Eisaki; D. H. Lu; Zhi-Xun Shen; Changyoung Kim


Bulletin of the American Physical Society | 2015

Investigation of Observating the role of orbital angular momentum with in Rashba and Dresselhaus effects system

Soohyun Cho; Wonsig Jung; Beomyoung Kim; Garam Han; M. Leandersson; Balasubramanian Thiagarajan; Changyoung Kim


arXiv: Mesoscale and Nanoscale Physics | 2014

Orbital angular momentum driven intrinsic spin Hall effect

Wonsig Jung; Dongwook Go; Hyun-Woo Lee; Changyoung Kim


Bulletin of the American Physical Society | 2014

ARPES study on annealing induced doping effects in electron doped cuprates

Dongjoon Song; Y. K. Kim; Wonsig Jung; Yoonyoung Koh; Wonshik Kyung; Garam Han; Beomyoung Kim; H. Eisaki; Yoshiyuki Yoshida; Seung-Ryong Park; C. Kim


Bulletin of the American Physical Society | 2014

Evidence for coexistence of Rashba and Dresselhaus effect on semiconductor

Wonsig Jung; S.H. Jo; Byung-Chang Kim; M. Leandersson; Balasubramanian Thiagarajan; Jisook Hong; Ji Hoon Shim; Changyoung Kim

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Y. K. Kim

Lawrence Berkeley National Laboratory

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C. Kim

Seoul National University

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Kenya Shimada

Synchrotron Radiation Center

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Panjin Kim

Sungkyunkwan University

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