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Electrodynamic properties of the semimetallic Dirac materialSrMnBi2: Two-carrier-model analysis
Park, H. J.,Park, Byung Cheol,Lee, Min-Cheol,Jeong, D. W.,Park, Joonbum,Kim, Jun Sung,Ji, Hyo Seok,Shim, J. H.,Kim, K. W.,Moon, S. J.,Kim, Hyeong-Do,Cho, Deok-Yong,Noh, T. W. American Physical Society 2017 Physical Review B Vol.96 No.15
<P>The electrodynamics of free carriers in the semimetallic Dirac material SrMnBi2 was investigated using optical spectroscopy and first-principles calculations. Using a two-carrier-model analysis, the total free-carrier response was successfully decomposed into individual contributions from Dirac fermions and non-Dirac free carriers. Possible roles of chiral pseudospin, spin-orbit interaction (SOI), antiferromagnetism, and electron-phonon (e-ph) coupling in the Dirac fermion transport were also addressed. The Dirac fermions possess a low scattering rate of similar to 10 meV at low temperature and thereby experience coherent transport. However, at high temperatures, we observed that the Dirac fermion transport becomes significantly incoherent, possibly due to strong e-ph interactions. The SOI-induced gap and antiferromagnetism play minor roles in the electrodynamics of the free carriers in SrMnBi2. We also observed a seemingly optical-gap-like feature near 120 meV, which emerges at low temperatures but becomes filled in with increasing temperature. This gap-filling phenomenon is ascribed to phonon-assisted indirect transitions promoted at high temperatures.</P>
Choi, Young Gwan,Zhung, Chan June,Park, Sun-Hee,Park, Joonbum,Kim, Jun Sung,Kim, Seongheun,Park, Jaehun,Lee, J. S. American Physical Society 2018 Physical review. B Vol.97 No.7
<P>Using optical-pump terahertz-probe spectroscopy, we investigated an ultrafast photocarrier relaxation behavior in a Bi1.5Sb0.5Te1.7Se1.3 (BSTS) single crystal, which is one of the most bulk-insulating topological insulators. Compared to n-type bulk-metallic Bi2Se3, we found that BSTS endows distinct behaviors in its photocarrier dynamics; the relaxation time turns out to be an order of magnitude longer, and the transient conductance spectrum exhibits a nonlinear increase as a function of the pumping power. Also, we observed an abrupt reduction of the photocarrier scattering rate in several picoseconds after the initial photoexcitation. We discuss these intriguing experimental observations based on a bulk-to-surface carrier injection assisted by the built-in electric field near the surface and electron-phonon scattering.</P>
Perforation of Membrane Envelope of Influenza A Virus by a Ganglioside-embedded Nanoparticle
Seokoh MOON,Byoungjae KONG,Yuna KIM,Younghun JUNG,Seok-Hyeon YU,Choongjin BAN,Jonghyeok SHIN,Joonbum PARK,Myungseo PARK,Chakhee KIM,Hooyeon KIM,Sora CHO,Yunjeong PARK,Hye Rin KIM,Hyun Seok OH,Jin Kyeo 한국생물공학회 2018 한국생물공학회 학술대회 Vol.2018 No.10