|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).
|342||Aug. 16 (Wed.), 4 PM||#1322 (E6-2. 1st fl.)||Prof. Noejung Park (UNIST)||Phonon-driven spin-Floquet valleytro-magnetism|
|341||Mar. 24 (Fri.), 4:00 PM||#1323 (1st fl. E6-2)||Dr. SangWook Lee||Graphene based nano electronics and nano electromechanics; focusing on precise control of nano structures for studying accurate physical properties|
|340||Mar. 24 (Fri.), 2:30 PM||#1323 (1st fl. E6-2).||Dr. MahnSoo Choi||Topological Dynamics|
|339||Nov. 3 (Fri.), 4:00 PM||#1323 (1st fl., E6-2.)||Dr. SungDae Ji (Max Planck POSTECH/Hshinchu Center (MPK))||Expedition to the Kitaev Quantum Spin Liquid: Hunting for Majorana fermions|
|338||Nov. 3 (Fri.), 2:30 PM||#1323 (1st fl., E6-2.)||Dr. MinChul Lee(Department of Applied Physics, Kyung Hee Univ.)||Quantum Resistor-Capacitor Circuit with Majorana Edge States|
|337||June 14, 2016 (Tue) 3PM||#1323 (E6-2 1st fl.)||Prof. Seungyong Hahn, Florida State University||No-Insulation High Temperature Superconductor Magnet Technology for Compact, Reliable, and Low-Cost High Field DC Magnets|
|336||October 31 (Thu.), 10:00am||#1323 (E6-2, 1st fl.)||Dr. Seung-Sup Lee||Kondo meets Hubbard: Impurity physics for correlated lattices|
|335||October 29 (Tue.), 4:00pm||#1323 (E6-2, 1st fl.)||Dr. Seung-Joo Lee||Particles and Gravity via String Geometry|
|334||October 29 (Tue.), 10:00am||#1323 (E6-2, 1st fl.)||Prof. Se Kwon Kim||Unconventional Spin Transport in Quantum Materials|
|333||October 16 (Wed), 4:00pm||#1323 (E6-2, 1st fl.)||Dr. Jaewon Song||Emergent black holes and monopoles from quantum fields|
|332||April 11 (Wed), 4:00pm||#1323 (E6-2, 1st fl.)||Dr. Young-Sik Ra||Non-Gaussian states of multimode light generated via hybrid quantum information processing|
|331||April 11 (Wed), 1:30pm||#1323 (E6-2, 1st fl.)||Dr. Yongsoo Yang||Probing 3D Structure and Physical Properties of Materials at the Single-Atom Level|
|330||April 13 (Fri.), 10am||#1323 (E6-2, 1st fl.)||Dr. Sungkun Hong||Quantum meets Mechanics: from Quantum Information to Fundamental Research|
|329||Nov. 28 (Tue.), 4:00 PM||#1323 (E6-2. 1st fl.)||Samindranath Mitra, Editor at Physical Review Letters||Physics after the lab and the desk: Your work in PRL|
|»||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|
|327||Sep. 13 (Wed.), 4 PM||#1323 (E6-2. 1st fl.)||Prof. Yi. Zhou (The Zhejiang Univ.)||An Introduction to Quantum Spin Liquids|
|326||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|
|325||July. 14 (Fri.), 3:00 PM||#1323 (E6-2. 1st fl.)||Dr. Jun Hyun Lee / University of Maryland||Chiral anomaly in disordered Weyl semimetals|
|324||Jun. 2 (Fri.), 4:00 PM||#1323 (E6-2. 1st fl.)||Dr. Sang Wook Kim||Maxwell's demon in quantum wonderland|
|323||Apr. 28 (Fri.), 04:00 PM||#1323 (E6-2. 1st fl.)||Dr. Minkyung Jung Research Institute, DGIST||Carbon nanotubes coupled to superconducting impedance matching circuits|