|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).
|공지||2019/03/21 - 5/30||Seminar Room #1323||Dr. Hyangtag Lim (KIST) and etc.||Spring 2019: Physics Seminar Serises|
|공지||2019/02/25 - 06/03||Seminar Room 1501||양용수 교수 (Prof. Yongsoo Yang, KAIST) and etc.||Spring 2019: Physics Colloquium|
|30||2015/08/04, 11PM||B501, Room Red, KI bldg. 5nd fl.||Dr. Eric Jin Ser Lee(Univ. of Manitoba, Canada)||Propagation of ultrasound through two- and three-dimensional strongly scattering media|
|29||October 18 (Thu.), 10:00 AM||#1323, E6-2||Dr. Duyoung Min||Understanding membrane protein folding using single-molecule force techniques|
|28||#1323(E6-2. 1st fl.)||Jul. 10th (Mon), 4pm||Dr. Duk Young Kim Los Alamos National Laboratory||“Intertwined Orders in a Heavy-fermion metal”|
|27||Nov. 9 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. Donghun Lee||Quantum sensing and imaging with diamond defect centers for nano-scale spin physics|
|26||Nov. 04 (Fri), 3:00 PM||E6-2. #1323(1st fl.)||Dr. Dohun Kim, Department of Physics and Astronomy, SNU||Quantum information experiments using few electron spins in semiconductors|
|25||September 5 (Wed.), 16:00 PM||#1323, E6-2||Dr. Dirk Wulferding||Shining a light on fractional excitations|
|24||June 22 (Fri.), 04:00 PM||#1323, E6-2||Dr. Daniel Sando||Tuning functional properties of BiFeO3 films using strain and growth chemistry|
|23||Oct. 12 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. Daniel Kyungdeock Park||Quantum Advantage in Learning Parity with Noise|
|22||May 16, 2016 (Mon) 4PM||#1323(E6-2, 1st Fl.)||Dr. Daniel Bowring , Fermi National Accelerator Laboratory||Tuning microwave cavities with biased nonlinear dielectrics for axion searches|
|21||2015/11/19, 4PM||E6-2, #1323||Dr. Daesu Lee (University of Wisconsin-Madison)||Emergent Collective Phenomena and Functions at Reduced Dimensions|
|20||2015/12/02, 4PM||E6-2, #1323||Dr. Dae-Jeong Kim (Dept. of Physics and Astronomy, University of California, Irvine)||Samarium Hexaboride: Is it a Topological insulator?|
|19||Oct. 07 (Fri), 4:00 PM||E6-2. #1323(1st fl.)||Dr. Choong Hyun Kim,IBS-CCES, Seoul National University||“Tilt engineering of 4d and 5d transition metal oxides?”|
|18||Apr. 08 (Fri.), 4:00 PM||E6-2. 5st fl. #1501||Dr. Changyoung Kim, SEOUL NATIONAL UNIV.||Spectroscopic studies of iron-based superconductors : what have we learned?|
|17||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|
|16||Apr. 28 (Thu.) 3PM||#2501(E6-2. 2nd fl.)||Dr. Chang Hee Sohn, SEOUL NATIONAL UNIVERSITY||Lattice/Spin/Charge Coupling in 5d Pyrochlore Cd2Os2O7|
|15||Oct. 18 (Tue.), 1:30 PM||1st fl. #1323(E6-2)||Dr. Chan-Ho Yang, Department of Physics, KAIST||"Visualization of oxygen vacancy in motion and the interplay with electronic conduction"|
|14||JAN. 7 (Mon), 03:00 PM||E6-2. 2st fl. #2501||Dr. Byoung min Kang||Many-Body Invariants for Multipoles in Higher-Order Topological Insulators|
|13||Feb. 12 (Mon), 3:00pm||#C303, (Creation Hall 3F, KAIST Munji Campus)||Dr. Byeongsu Yang, Kamioka Observatory, Univ. of Tokyo||The recent result of XMASS Experiment|
|12||May 11 (Wed.), 4 PM||E6-2. #1323(1st fl.)||Dr. Bumjoon Kim, Max Planck Institute for Solid State Research||The quest for novel high-temperature superconductors---Prospects and progress in iridates|
|11||Jun 28, 14:00||E6-2, #1322||Dr. Bongjae Kim, Dr. Sooran Kim, Dr. Jeongwoon Hwang||1st Research-exchange meeting of computational material physics|