We investigate strongly correlated electron systems including high-transition temperature superconductors (Cu-oxide and Fe-based superconductors) and heavy Fermion systems, van der Waals 2D material systems including graphene and transition metal dichalcogenides, organic electronic materials including organic solar cells, and single crystal copper films. We are also interested in investigating new emerging quantum material systems including topological matters and room temperature superconductors under high-pressure.
Strongly correlated electron systems – high-Tc superconductors (cuprates and Fe pnictides), 3d & 5d transition metal oxides, heavy Fermion systems
[16] Temperature-dependent electronic evolution of f electrons of CeCoIn5 via a comparative infrared study with LaCoIn5; Myounghoon Lee, Yu-Seong Seo, Seulki Roh, Seokbae Lee, Jihyun Kim, Tuson Park, and Jungseek Hwang, Results in Physics 47, 106376/1-9 (2023).
[15] Bosonic spectrum of a correlated multiband system, BaFe1.80Co0.20As2, obtained via infrared spectroscopy; Chandan Kumar Panda, Hong Gu Lee, Hwiwoo Park, Soon-Gil Jung, Ki-Young Choi, and Jungseek Hwang, Results in Physics 50, 106572/1-6 (2023).
[14] Doping-dependent superconducting properties of K-doped BaFe2As2 via infrared spectroscopy; Seokbae Lee, Yu-Seong Seo, Seulki Roh, Dongjoon Song, Hiroshi Eisaki, and Jungseek Hwang, Scientific Reports 12, 19950/1-9 (2022).
[13] Superconducting coherence lengths of hole-doped cuprates obtained from electron-boson spectral density functions; Jungseek Hwang, Scientific Reports 11, 11668/1-7 (2021).
[12] Magnetic-ordering-driven metal-insulator transitions in quasi one-dimensional spin ladder compounds, BaFe2S3 and BaFe2Se3; Seulki Roh, Soohyeon Shin, Jaekyung Jang, Seokbae Lee, Myounghoon, Lee, Yu-Seong Seo, Weiwu Li, Tobias Biesner, Martin Dressel, Joo Yull Rhee, Tuson Park, and Jungseek Hwang, Physical Review B 101, 115118/1-5 (2020).
[11] Temperature-dependent optical properties of self-doped superconducting Fe-pnictide, Sr2VO3FeAs; Seokbae Lee, Seulki Roh, Yu-Seong Seo, Myounghoon Lee, Eilho Jung, Jongmok Ok, Myung-Chul Jung, Byungkyun Kang, Kwan-Woo Lee, Jun Sung Kim, and Jungseek Hwang, Journal of Physics: Condensed Matter 31, 445602/1-8(2019).
[10] Temperature-dependent excitonic superfluid plasma frequency evolution in the strong excitonic insulator candidate, Ta2NiSe5; Yu-Seong Seo, Man Jin Eom, Jun Sung Kim, Chang-Jong Kang, Byung Il Min, and Jungseek Hwang, Scientific Reports 8, 11961/1-9 (2018).
[9] Oxygen vacancy induced structural evolution of SrFeO3-x thin film from brownmillerite to perovskite; Seulki Roh, Seokbae Lee, Myounghoon Lee, Yu-Seong Seo, Amit Khare, Taesup Yoo, Sungmin Woo, Woo Seok Choi, and Jungseek Hwang, Physical Review B 97, 075104/1-8 (2018).
[8] Intrinsic temperature-dependent evolutions in the electron-boson spectral density obtained from optical data; Jungseek Hwang, Scientific Reports 6, 23647/1-12 (2016).
[7] Hidden non-Fermi lquid behavior caused by magnetic phase transition in Ni-doped Ba-122 pnictides; Seokbae Lee, Kiyoung Choi, Eilho Jung, Seulki Roh, Soohyeon Shin, Tuson Park, and Jungseek Hwang, Scientific Reports 5, 12156/1-9 (2015).
[6] Bosons in high-temperature superconductors: an experimental survey; Joules P. Carbotte, Thomas Timusk, and Jungseek Hwang, Reports on Progress in Physics 74, 066501/1-43 (2011).
[5] High-transition-temperature superconductivity in the absence of the magnetic resonance mode; J. Hwang, T. Timusk and G. D. Gu, Nature (London) 427, 714-717 (2004).
- M. Norman, News and Views, Nature 427, 692 (2004)
- Graham P. Collins, Scientific American, p28, May 2004
[4] Scanning-tunnelling spectra of cuprates; J. Hwang, T. Timusk and J. P. Carbotte, Nature (London) 446, E3-E4 Brief Communications Arising (8 March 2007).
[3] Evolution of the bosonic spectral density of the high-temperature superconductor Bi2Sr2CaCu2O8+d; J. Hwang, T. Timusk, E. Schachinger and J. P. Carbotte, Physical Review B 75, 144508/1-6 (2007) (*Selected for the May 1, 2007 issue of Virtual Journal of Applications of Superconductivity).
[2] Evidence for a pseudogap in underdoped Bi2Sr2CaCu2O8+d and YBa2Cu3O6.50 from in-plane optical conductivity measurements; J. Hwang, J. P. Carbotte and T. Timusk, Physical Review Letters 100, 177005/1-4 (2008) (*Selected for the May 1, 2008 issue of Virtual Journal of Applications of Superconductivity).
[1] Doping and temperature dependent optical properties of reduced BaTiO3-d; J. Hwang, T. Kolodiazhnyi, J. Yang and M. Couillard, Physical Review B 82, 214109/1-8 (2010).
Topological matters
[1] Kagome metals
Low dimensional systems – van der Waals 2D materials (graphene, transition metal dichalcogenides, etc)
[6] Robust excitonic insulating states in Cu-substituted Ta2NiSe5; Junseong Song, Eilho Jung, Byeong Wook Cho, Bumsub Song, Jae Woo Kim, Hyeonbeom Kim, Ki Kang Kim, Byoungchul Son, Jouhahn Lee, Jungseek Hwang, and Young Hee Lee, Advanced Materials Interfaces 10, 2300010/1-8 (2023).
[5] Evidence of Shallow Bandgap in Ultra-thin 1T’-MoTe2 via Infrared Spectroscopy; Jincheol Park, Eilho Jung, Sanghyun Lee, Jungseek Hwang, and Younghee Lee, Physical Review B 101, 235434/1-7 (2020).
[4] Optical properties of graphite oxide and reduced graphite oxide; Eilho Jung, Seokbae Lee, Seulki Roh, Eunhee Hwang, Junghyun Lee, Hyoyoung Lee and Jungseek Hwang, Journal of Physics D: Applied Physics 47, 265306/1-6 (2014).
[3] Ultrapure Multilayer Graphene in Bromine Intercalated Graphite; J. Hwang, J. P. Carbotte, S. Tongay, A. Hebard, and D. B. Tanner, Physical Review B (Rapid Communications) 84, 041410(R)/1-4 (2011); selected as Editor’s Suggestions.
[2] Supermetallic Conductivity in Br-intercalated Graphite; S. Tongay, J. Hwang, D. B. Tanner, H. K. Pal, D. Maslov and A. Hebard, Physical Review B 81, 115428/1-6(2010).
[1] Polarized spectroscopy of aligned single wall carbon nanotubes; J. Hwang, H. H. Gommans, A. Ugawa, H. Tashiro, R. Haggenmueller, K. I. Winey, J. E. Fischer, D. B. Tanner and A. G. Rinzler, Physical Review B (Rapid Communications) 62, R13310-R13313 (2000).
Organic electronic materials – conductive polymers and organic solar cells
[7] Modulation spectroscopy study on additive-induced efficiency enhancement of PTB7:PC71BM organic photovoltaic devices, Sangheon Park, Yu-Seong Seo, Won Suk Shin, Dae Joon Kang, and Jungseek Hwang, Current Applied Physics 25, 48-54 (2021).
[6] Temperature-dependent Optical Properties of Hybrid Organic-Inorganic Perovskite Single Crystals: CH3NH3PbI3 and CH3NH3PbBr3; Sangheon Park, Yu-Seong Seo, Chang Won Ahn, Won Seok Woo, Jihoon Kyhm, Ill Won Kim, and Jungseek Hwang, Journal of Physics D: Applied Physics 52, 335302/1-10 (2019).
[5] Rapid and Checkable Electrical Post-Treatment Method for Organic Photovoltaic Devices; Sangheon Park, Yu-Seong Seo, Won Suk Shin, Sang-Jin Moon, and Jungseek Hwang, Scientific Reports 6, 22604/1-8 (2016).
[4] In-situ measurements of the optical absorption of dioxythiophene-based conjugated polymers; J. Hwang, I. Schwendeman, B. C. Ihas, R. J. Clark, M. Cornick, M. Nikolou, A. Argun, J. R. Reynolds and D. B. Tanner, Physical Review B 83, 195121/1-12 (2011).
[3] Optical properties of nondegenerate ground state polymers: Three dioxythiophene-based conjugated polymers, J. Hwang, D. B. Tanner, I. Schwendeamn and J. R. Reynolds, Physical Review B 67, 115205/1-10 (2003).
[2] Combined Visible and Infrared Electrochromism Using Dual Polymer Devices; I. Giurgiu, J. Hwang, D. M. Welsh, D. B. Tanner and J. R. Reynolds, Advanced Materials 13, 634-637 (2001).
[1] Multicolored electrochromism polymers: Structures and devices (Invited for special edition on Organic Electronics); Argun AA, Aubert PH, Thompson BC, Schwendeman I, Gaupp CL, Hwang J, Pinto NJ, Tanner DB, MacDiarmid AG and Reynolds JR, Chemistry of Materials 16, 4401-4412 (2004).
Single crystal copper thin film
[3] Self-oxidation resistance of the curved surface of achromatic copper; Young-Hoon Kim, Seong-Gon Kim, Seunghun Lee, Miyeon Cheon, Su Jae Kim, Kideuk Nam, Bipin Lamichhane, Sung Heum Park, Min-Hyoung Jung, Ji-Soo Kim, Hu Young Jeong, Yusil Lee, Yu-Seong Seo, Jungseek Hwang, Young Hee Lee, Young-Min Kim, and Se-Young Jeong, Advanced Materials 2023, 2210564/1-10 (2023).
[2] Coherent consolidation of trillions of nucleations into a coplanar layer aimed a mono-atom step-level flat surface; Taewoo Ha, Yu-Seong Seo, Teun–Teun Kim, Bipin Lamichhane, Young-Hoon Kim, Su Jae Kim, Yousil Lee, Miyeon Cheon, Jong Chan Kim, Sang Eon Park, Kyung Ik Sim, Jae Hoon Kim, Yong In Kim, Seon Je Kim, Hu Young Jeong, Young Hee Lee, Seong-Gon Kim, Young-Min Kim, Jungseek Hwang, and Se–Young Jeong, Nature Communications 14, 685 /1-9 (2023).
[1] Color of Copper/Copper Oxide; Su Jae Kim, Jegon Lee, Yu-Seong Seo, Myounghoon Lee, Yousil Lee, Chae Ryong Cho, Jong-pil Kim, Miyeon Cheon, Jungseek Hwang, Woo Seok Choi, Se-Young Jeong, and Young Hee Lee, Advanced Materials 33, 2007345/1-7 (2021).