|장소||#1323 (E6-2. 1st fl.)|
|일시||Sep. 26 (Tue.), 11AM|
|연사||Dr. Yukiaki Ishida / ISSP, University of Tokyo|
Time-resolved ARPES study of Dirac and topological materials
Dr. Yukiaki Ishida / ISSP, University of Tokyo
Sep. 26 (Tue.), 11AM
#1323 (E6-2. 1st fl.)
Time- and angle-resolved photoemission spectroscopy (TARPES) has become a powerful tool to investigate the non-equilibrated states and dynamics of matter from an electronic structural point of view. Being a surface sensitive method, TARPES has also opened pathways to explore the ultrafast phenomena occurring on the edge of matter. We present investigations done on Dirac and topological materials by using a TARPES apparatus that achieves the energy resolution of 10.5 meV and high stability .
1. Classification of the topological phase of matter:
In 2008, it was demonstrated that there are two classes in non-magnetic insulators. A topological twist can be defined for the bulk band structure, and those that have the twist belong to the topologically-nontrivial class. The effect of the twist appears on the edge: On surface of topological insulators (TIs), novel Dirac-type dispersion is formed. Thus, the classification can be done by investigating whether the surface Dirac dispersion exists or not.
2. Functioning surface of topological insulators by light:
We discovered that surface photo-voltage (SPV) can emerge on TIs when the bulk is sufficiently insulating . That is, TIs now meet the well-known opto-electronic function of semiconductors. We discuss that the SPV effect can be utilized to generate spin-polarized current on TI surface, and present the ongoing research towards this end.
3. Ultrafast dynamics of Dirac electrons:
Massless Dirac fermions have the ability to absorb light of whatever color. Thus, Dirac fermions are prospective in opto-electronics. In fact, ultrashort pulses of any color can be created by using TIs and graphitic materials. Broad-band lasing may also be realized if a population inversion can be formed across the Dirac point. Firm understanding of the Dirac electron dynamics thus becomes of paramount importance. We show that an inverted population is realized in the surface Dirac band of a TI Sb2Te3 . Dynamics being either within or beyond a simple two-temperature model scheme is observed in layered Dirac semimetals such as graphite and SrMnBi2 .
 Y. Ishida et al., Rev. Sci. Instrum. 85, 123904 (2014); Y. Ishida et al., Sci. Rep. 6, 18747 (2016).
 P. Zhang et al., Phys. Rev. Lett. 118, 046802 (2017).
 S. Kim et al., Phys. Rev. Lett. 112, 136802 (2014).
 I. Belopolski et al., Nature Commun. 7, 13643 (2016).
 Y. Ishida et al., Sci. Rep. 5, 8160 (2015); M. Neupane et al., Phys. Rev. Lett. 115, 116801 (2015).
 S. Zhu et al., Sci. Rep. 5, 13213 (2015).
 Y. Ishida et al., Sci. Rep. 1, 64 (2011); Y. Ishida et al., Phys. Rev. B 93, 100302(R) (2016).
|27||Sep. 02(Fri) 4:00 PM||E6-2(1st fl) #1323||Dr. Yong-Joo Doh, Department of Physics and Photon Science, GIST||Quantum Electrical Transport in Topological Insulator Nanowires|
|26||Sep. 10 (Tue.), 03:00 PM||E6-2. 1st fl. #1323||Dr. Mikhail Kiselev||Two-Stage Kondo Effect|
|25||Sep. 11(Fri), 14:00~||zoom||이관형교수/SNU, 이상윤교수/GIST||SRC Seminar|
|24||Sep. 12 (Tue.), 4 PM||#1323 (E6-2. 1st fl.)||Prof. Yi. Zhou (The Zhejiang Univ.)||Exact Solution for the Interacting Kitaev Chain at Symmetric Point|
|23||Sep. 13 (Wed.), 4 PM||#1323 (E6-2. 1st fl.)||Prof. Yi. Zhou (The Zhejiang Univ.)||An Introduction to Quantum Spin Liquids|
|22||Sep. 14(Mon) 17:30~||Zoom webinar||Teruo Ono (Kyoto U. Japan)||KAIST Global Forum for Spin and Beyond (Third Forum)|
|21||Sep. 22 (Fri.), 01:00 PM||E6-2. 1st fl. #1323||Dr. EunSeong Kim / Department of Physics, KAIST||Superconductor-metal-insulator transition in thin Tantalum films|
|20||Sep. 22 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. GilHo Lee / Department of Physics, POSTECH||Quantum Electronic Transport in Graphene Hybrid Nanostructures|
|19||Sep. 22 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. GilHo Lee / Department of Physics, POSTECH||Unexpected Electron-Pairing in Integer Quantum Hall Effect|
|18||Sep. 22, 2016(Thu), 3:30 PM||#1323(E6-2, 1st fl.)||Dr. Haiyang Yan (Institute of Nuclear Physics and Chemistry)||Polarized 3He, Polarized Neutrons and New Interactions beyond the Standard Model|
|17||Sep. 22, 2016(Thu), 3:30 PM||#1323(E6-2, 1st fl.)||Dr. Haiyang Yan (Institute of Nuclear Physics and Chemistry)||Polarized 3He, Polarized Neutrons and New Interactions beyond the Standard Model|
|16||Sep. 22nd 9:30 AM||Zoom webinar||Prof. Xu Yi (Univ. of Virginia, USA)||Physics and applications of soliton microcombs(Quantum- & Nano-Photonics)|
|15||Sep. 24(Thu), 09:00~, Sep. 24(Thu), 16:00 ~||Zoom Video||Akash V. Dixit (University of Chicago), Dr. Boris Ivanov (Novosibirsk State Technical University)||(CAPP/IBS)Searching for Dark Matter with a Superconducting Qubit , Cryogenic Microwave Circuit Development at the NSTU|
|»||Sep. 26 (Tue.), 11AM||#1323 (E6-2. 1st fl.)||Dr. Yukiaki Ishida / ISSP, University of Tokyo||Time-resolved ARPES study of Dirac and topological materials|
|13||Sep. 27 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. Joon Sue Lee||Spin-charge conversion in topological insulators for spintronic applications|
|12||Sep. 27 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. Jindong Song||0D/1D/2D/3D III-V materials grown by MBE for Optelectronics|
|11||Sep. 29 (Thu), 4:00 PM||E6-2. #2501(2nd fl.)||Dr. Minu Kim, Institute for Basic Science, Seoul National University||Exploring the phase diagram of BaBiO3: epic voyage of just another bad trip?|
|10||Sep. 29th(Thu), 4PM||E6-2 #1323 (1st floor)||Dr. Sangyoon Han, Department of Physics, KAIST||Large-scale Silicon Photonic MEMS Switches|
|9||Sep. 4 (Tue), 02:30 PM||E6-2. 2st fl. #2502||Dr. Changmin Lee, MIT||Ultrafast time- and angle-resolved photoemission spectroscopy (tr-ARPES) with extreme ultraviolet laser pulses|
|8||Sep.28. 5:30 pm||Zoom webinar||Burkard Hillebrands (TU Kaiserslautern, Germany)||KAIST Global Forum for Spin and Beyond(Fourth Forum)|