초전도 현상은 양자 현상이 거시적으로 관찰되는 유일하고 흥미로운 현상이다. 초전도체가 가지는 특이 한 전기적, 자기적, 양자 특성으로 인해 그 응용분야는 무궁무진하다. 초전도 연구실에서는 다양한 초전 도체를 제작하고 초전도 특성을 비롯한 다양한 물성에 대해 연구한다. 특히 전력분야 응용을 위한 전류 수송 능력 향상을 위해 자기소용돌이 거동에 대해 집중적으로 연구하고 있다.

1. Flux pinning property of ReBCO (Re=rare earth) high-temperature superconducting thin films
   ReBCO high-temperature superconductors have a higher critical temperature and better critical current density characteristics under magnetic fields compared to YBCO, making them highly useful for power applications. Due to their high structural anisotropy, manufactured in thin film form, the superconducting properties, including critical current density, can be maximized. Given the characteristics of second-generation superconductors, the presence of appropriate flux pinning centers can increase both the critical current and the critical magnetic field, which is why research is being conducted on adding various forms of artificial flux pinning centers. In particular, research is being conducted on using buffer layers to exploit the strain caused by lattice constant mismatches between the substrate, buffer layer, and superconducting layers as flux pinning centers
    
    
    
2. 2. Development of buffer layer for the MgB2 superconducting tapes
   MgB₂ superconductor, whose superconductivity was discovered relatively recently, has a simple structure that makes it easy to manufacture, but its critical temperature reaches ~40 K, leading to expanded applications including in the medical field. Despite its simple structure, the Fermi surface has a complex form with two superconducting gaps and the two superconducting bands. It belongs to the class of non-conventional superconductors and has the characteristic that superconductivity can be controlled through selective doping in the two superconducting bands. Due to its structural anisotropy, when manufactured in thin film form, superconducting properties including the critical current density are greatly improved. To manufacture it in thin film form on flexible metal substrates for power applications, appropriate buffer layers are essential to prevent delamination and the penetration of superconductivity into the metal.
    
    
3. Flux pinning property of Bi-based high-temperature superconductor (Bi-2223)
   The Bi-based superconductor shows an increase in structural anisotropy and the critical temperature with the number of CuO₂ planes, where Bi-2201 has the critical temperature of 50 K, Bi-2212 has 70 K, and Bi-2223 has ~100 K. Among these, Bi-2223, with a critical temperature above liquid nitrogen, is the most prominent in applications. Research is being conducted to improve the flux pinning properties by adding appropriate flux pinning centers. In our lab, studies on the local structure using XAS (X-ray Absorption Spectroscopy) are conducted to understand the enhancement and variation of superconductivity by adding various second phases.
    

PUBLICATION LIST
1. R. P. Putra, J. Y. Oh, G. H. An, I. N. Rahman, H. S. Lee, and Byeongwon Kang*, “Raman Spectroscopy Investigation of Phonon Behavior in ZnO-Buffered MgB2 Tapes: Exploring Lattice Dynamics and Anharmonicity”, JOURNAL OF PHYSICAL CHEMISTRY LETTERS 15, 8924 (2024)
2. Han-Seok Park, Jun-Yung Oh, and Byeongwon Kang*, “Exploring Structural Features and Growth Mechanisms in GdBa2Cu3O7−x/LaFeO3 Bilayers on SrTiO3 Substrates”, ACS OMEGA 9, 26560 (2024)
3. R. P. Putra, J. Y. Oh, M. A. Anugrah, T. Miyanaga, and Byeongwon Kang*, “Evidence of disordered local structure of ZnO buffered MgB2 films via Polarized extended X-ray absorption fine structure analysis”, APPLIED SURFACE SCIENCE 663, 160210 (2024)
4. R. P. Putra, J. Y. Oh, G. H. An, H. S. Lee, and Byeongwon Kang*, “Investigation on the phonon behavior of MgB2 films via polarized Raman spectra”, PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 26(1), 14 (2024)
5. Jun-Yung Oh, Dong-Seok Yang and Byeongwon Kang*, “Local instability in GdBa2Cu3O7-x/La0.7Sr0.3MnO3 superconducting bilayer: Temperature-dependent EXAFS study”, CERAMICS INTERNATIONAL 49, 25767 (2023)
6. M. A. Anugrah, R. P. Putra, J. Y. Oh, and B Byeongwon Kang*, “Effect of La0.7Sr0.3MnO3 addition on superconducting properties and local structure of (Bi, Pb)-2223 superconductor”, PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 25(2), 5 (2023)
7. Rico P. Putra, Jun Yung Oh, Sun Gil Jung, Han Seok Park, Won Nam Kang, and Byeongwon Kang*, “Enhancement in High-Field Jc Properties and the Flux Pinning Mechanism of ZnO-Buffered MgB2 Films”, ACS OMEGA 8, 11607 (2023)
8. Seunghyun Lee, Daseul Jeong, Sriram KK, Shangzhi Chen, Fredrik Westerlund, Byeongwon Kang, Kyoung-Ho Kim, Magnus P. Jonsson and Evan S. H. Kang*, “Plasmonic polymer nanoantenna arrays for electrically tunable and electrode-free metasurfaces”, JOURNAL OF MATERIALS CHEMISTRY A, 11 21569 (2023)
9. R. P. Putra, Y. S. Lee, J. Y. Oh, L. M. Tien, W. N. Kang, T. Miyanaga, and Byeongwon Kang*, “Correlation between Tc and local structure of MgB2 films with ZnO buffer layer: X-ray absorption fine structure study”, PHYSICA B 645, 414234 (2022)
10. Byeong-Heon Song, Jun-Yung Oh, Han-Seok Park and Byeongwon Kang*, “Effect of La1-xSrxMnO3(x=0.2, 0.3, 0.5) buffer layer on the superconducting properties of GdBa2Cu3O7-”, JOURNAL OF THE KOREAN PHYSICAL SOCIETY 81, 770-778 (2022)
11. J. Y. Oh, Y. J. Ko, D. S. Yang, W. S. Jeong, and Byeongwon Kang*, “Strain engineering using La0.7Sr0.3MnO3 buffer layer for enhancing superconductivity in GdBa2Cu3O7-x films”, JOURNAL OF MATERIALS SCIENCE: MATERIALS IN ELCTRONICS 33, 15272 (2022)
12. J. Y. Oh, D. S. Yang, and Byeongwon Kang*, “Effect of competition between superconductivity and ferromagnetism in GdBa2Cu3O7-x/La0.7Sr0.3MnO3 bilayers”, PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 24 (2), 19-22 (2022)
13. Wanseop Jeong, Hyun Sik Kim*, Byeongwon Kang*, “Development of a portable time-of-flight mass spectrometer prototype using a cold electron source”, REVIEW OF SCIENTIFIC INSTRUMENTS 93, 023302 (2022)
14. J. Y. Oh, D. S. Yang, W. N. Kang, and Byeongwon Kang*, “Competition between ferromagnetism and superconductivity in GdBa2Cu3O7-x/La0.7Sr0.3MnO3 bilayers with varying thickness”, CERAMICS INTERNATIONAL 48(1), 1068 (2022)
15. J. Y. Oh, Y. J. Ko, D. S. Yang, J. M. Lee, W. N. Kang, and Byeongwon Kang*, “Tuning Flux Pinning in GdBa2Cu3O7−x/La0.7Sr0.3MnO3 Epitaxial Bilayers via Substrate-Induced Strain”, CRYSTAL GROWTH & DESIGN 21, 4473 (2021)
16. H. T. Lee, G. S. Ji, J. Y. Oh, C. W. Seo, Byeongwon Kang, K. W. Kim, and H. R. Park* , “Measuring Complex Refractive Indices of a Nanometer-Thick Superconducting Film Using Terahertz Time-Domain Spectroscopy with a 10 Femtoseconds Pulse Laser”, CRYSTALS 11, 6512 (2021)
17. H. S. Park, B. H. Song, J. Y. Oh, and Byeongwon Kang*, “Structural suitability of GdFeO3 as a magnetic buffer layer for GdBa2Cu3O7-x superconducting thin films", PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 23(2), 14 (2021)
18. R P Putra, Y S Lee, P Doung, Y J Ko, W N Kang, K-H Kim, Byeongwon Kang*, “Electron-phonon coupling behavior in MgB2 films with various thicknesses of ZnO buffer layer on metallic substrates”, SOLID STATE COMMUNICATIONS 323, 114117 (2021)
19. J Y Oh, C Y Song, Y J Ko, J M Lee, W N Kang, D S Yang and Byeongwon Kang*, “Strong correlation between flux pinning and epitaxial strain in the GdBa2Cu3O7x/La0.7Sr0.3MnO3 nanocrystalline heterostructure”, RSC ADVANCES 10, 39102 (2020)
20. J Y Oh, C Y Song, Y J Ko, D S Yang and Byeongwon Kang*, “Strain-induced local structural change and its effect on the superconducting properties of GdBa2Cu3O7-x /La0.7Sr0.3MnO3 heterostructure”, SUPERCONDUCTOR SCIENCE and TECHNOLOGY 33(7), 075002 (2020)
21. J Y Oh, D S Yang, D H Tran and Byeongwon Kang*, “Influences of Na-doping on valence states and interatomic potential in Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconductor”, CERAMICS INTERNATIONAL, 46(6) 8259-8263 (2020)
22. C. Y. Song, J. Y. Oh, Y. J. Ko, J. M. Lee, W. N. Kang, and Byeongwon Kang*, “Enhanced flux pinning property of GdBa2Cu3O7-x films by ferromagnetic surface decoration”, PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 22(2), 21 (2020)
23. J Y Oh, T M Le, A T Pham, D H Tran, D S Yang and Byeongwon Kang*, “Role of interlayer coupling in alkaline-substituted (Bi, Pb)-2223 superconductors”, JOURNAL OF ALLOYS AND COMPOUNDS 804(5):348-352 (2019)
24. J.Y. OH, A.T. Pham, D.H. Tran, D.S. Yang, and Byeongwon Kang*, “Effect of K Substitution on Local Structure of Bi1.6Pb0.4Sr2-xKxCa2Cu3O10+δ System Probed by Extended X-Ray Absorption Fine Structure”, JOURNAL OF ELECTRONIC MATERIALS 48(8) 4920-4924 (2019)
25. J. Y. Oh W. N. Kang Byeongwon Kang*, “Flux Pinning Mechanism in BaSnO3-Added GdBa2Cu3O7-x Films with Different Thickness”, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 32, 3165-3170 (2019)
26. Byeongwon Kang*, W B K Putri and W N Kang, “Effect of SiC buffer layer on flux pinning property of MgB2 tapes”, CURRENT APPLIED PHYSICS 19, 670-674 (2019)
27. Y. J. Ko, J. Y. Oh, C. Y. Song, D. S. Yang, D. H. Tran, and Byeongwon Kang*, “Phase transition of (Bi, Pb)-2223 superconductor induced by Fe3O4 addition”, PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 21(4), 1 (2019)
28. Byeongwon Kang*, D H Tran and W N Kang, “Scaling of pinning forces in BaSnO3-added GdBa2Cu3O7−x superconducting thin films”, THIN SOLID FILMS 624, 16-20 (2017)
29. J. K. Lee, J. Y. Oh, J. M. Lee, W. N. Kang, and Byeongwon Kang*, “The flux pinning properties of BaSnO3-added GdBa2Cu3O7-δ films with varying growth conditions”, PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 19(3), 18 (2017)
30. J. Y. Oh, H. K. Jeon, J. M. Lee, W. N. Kang, and Byeongwon Kang*, “Effect of double pinning mechanism in BSO-added GdBa2Cu3O7-x thin films”, PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 19(3), 13 (2017)
31. W B K Putri, P V Duong, W N Kang, T Miyanaga, D S Yang and Byeongwon Kang*, “Close relation between Mg–Mg bonds and Tc of SiC buffered-MgB2 tapes”, JOURNAL OF ALLOYS AND COMPOUNDS 665, 352 (2016)
32. H. K. Jeon, J. K. Lee, D. S. Yang, W. N. Kang, and Byeongwon Kang*, “Effect of BSO addition on Cu-O bond of GdBa2Cu3O7-x films with varying thickness probed by extended x-ray absorption fine structure”, PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 18(4), 1 (2016)
33. Witha Berlian Kesuma Putri, Byeongwon Kang*, Pham Van Duong, Won Nam Kang, “Reducing delamination in MgB2 films deposited on Hastelloy tapes by applying SiC buffer layers”, THIN SOLID FILMS 590, 80-83 (2015)
34. W. B. K. Putri, Byeongwon Kang*, P. V. Duong, and W. N. Kang, “Superconducting properties of SiC-buffered-MgB2 tapes”, PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 17(3), 1 (2015)
35. Duc H. Tran, Witha B. K. Putri, Byeongwon Kang,*, Nam Hoon Lee, and Won Nam Kang, “The critical current density of GdBCO superconducting films: thickness, temperature, and field dependence”, IEEE TRANSACTIONS ON MAGNETICS 50 (6) 9000404 (2014)
36. Witha B. K. Putri, Duc Hai Tran, Byeongwon Kang*, Mahipal Ranot, Jae Hak Lee, Nam Hoon Lee, and Won Nam Kang, “Effect of different thickness crystalline SiC-buffer layers on superconducting properties and flux pinning mechanism of MgB2 films”, IEEE TRANSACTIONS ON MAGNETICS 50 (6) 9000305 (2014)
37. D H Tran, W B K Putri, Byeongwon Kang*, N H Lee, and W N Kang, “A close correlation between nanostructure formations and the thickness dependence of the critical current density in pure and BaSnO3-added YBa2Cu3O7-x films”, JOURNAL OF APPLIED PHYSICS 115, 163901 (2014)
38. W B K Putri, D H Tran, O Y Lee, W N Kang, T Miyanaga, D S Yang, and Byeongwon Kang*, “Effect of different thickness crystalline SiC buffer layers on the ordering of MgB2 films probed by extended x-ray absorption fine structure”, JOURNAL OF APPLIED PHYSICS 115, 093901 (2014)
39. Yeong Seon Lee and Byeongwon Kang*, “Resonance tunneling phenomena by periodic potential in type-II superconductor”, PROGRESS IN SUPERCONDUCTIVITY AND CRYOGENICS (PSAC) 16(1), 1 (2014)