|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).
|228||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|
|227||April 13 (Fri.), 10am||#1323 (E6-2, 1st fl.)||Dr. Sungkun Hong||Quantum meets Mechanics: from Quantum Information to Fundamental Research|
|226||May 1 (Wed), 4:00 PM||#1323, E6-2||Dr. Sungkyun Choi||Raman and x-ray scattering study on correlated electron systems: two case examples|
|225||May. 25(Wed), 4pm||E6-2. 1st fl. #1323 / Zoom||Dr. Sungwoo Hong (Enrico Fermi Institute at University of Chicago)||Uncovering New Lampposts for Dark Matter: Continuum or Conformal|
|224||May. 11(Wed), 4pm||E6-2. #1323 & Zoom||Dr. Sunok Josephine Suh (Kavli Institute for Theoretical Physics)||Gravity as a phenomenon in quantum dynamics|
|223||2015/11/28, 10AM||E6-2, #1323||Dr. Suyong Jung (Korea Research Institute of Standards and Science)||Electron Tunneling Spectroscopy of Single and Bilayer Graphene with Hexagonal Boron Nitride as Tunneling Barrier|
|222||May. 14 (Fri.), 02:30 PM||Online seminar||Dr. Suyong Jung(KRISS)||Electrically tunable spin valve effect in vertical van-der-Waals magnetic tunnel junctions|
|221||Apr. 2 (Fri.), 02:30 PM||Online(Zoom)||Dr. Tae Hyun Kim (SNU)||Quantum computing and entanglement generation using trapped ions and photons|
|220||2016/03/11 4 PM||E6-2. 1st fl. #1501||Dr. Tae-Hwan KIM (POSTECH)||Jan. Switching handedness of of chiral solitons in Z4 topological insulators|
|219||Mar. 29 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. Taeyoung Choi||Coherent Quantum Control and Magnetism on atoms – Trapped ion and ESR STM|
|218||Jun. 18 (MON), 10:00 AM||E6-2. 2nd fl. #2502||Dr. Thibault VOGT||Rydberg electromagnetically induced transparency and microwave-to-optical conversion using Rydberg atoms|
|217||October 16 (Tue.), 10:00 AM||#1323, E6-2||Dr. Won-Ki Cho||Capturing protein cluster dynamics and gene expression output in live cells|
|216||2015/11/10, 4PM||E6-2, #1323||Dr. Woosuk Bang (Physics division, Los Alamos National Laboratory)||Rapid heating of matter using high power lasers|
|215||2015/12/01, 4PM||E6-2, #1323||Dr. Yeong Kwan Kim(Lawrence Berkeley National Laboratory, USA)||Introducing extra dimensions to spectroscopic studies of advanced quantum materials|
|214||Sep. 02(Fri) 2:30 PM||E6-2(1st fl.), #1323||Dr. Yong-Hyun Kim,Graduate School of Nanoscience and Technology, KAIST||Nanoscale Thermal Physics: Seebeck Effect and Nanoscale Friction|
|213||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|
|212||October 15 (Mon.), 16:00 PM||#1323, E6-2||Dr. Yongjoo Baek||Universal properties of macroscopic current-carrying systems|
|211||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|
|210||Jun. 10 (Fri.), 11:00 AM||Online seminar||Dr. Yoon Jang Chung(Laboratory for Physical Sciences, University of Maryland)||Record-quality two-dimensional electron systems|
|209||May. 13 (Fri.), 04:00 PM||자연과학동(E6-2) 1st fl. #1323||Dr. Yosep Kim(Center for Quantum Information, KIST)||High-fidelity iToffoli gate for fixed-frequency superconducting qubits|