|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||2017/09/14 - 12/07||Seminar Room #1323||Prof. 정광용 교수(Gacheon Univ) and etc.||Fall 2017: Physics Seminar Serises|
|공지||2017/09/04 - 12/04||Seminar Room 1501||Prof. Sangsu Bae(Hanyang Univ.) and etc.||Fall 2017: Physics Colloquium|
|149||5월 17일(화), 11:00 ~ 12:00||창의학습관(E11), 406호||방준혁 박사(Korea Basic Science Institute, KBSI)||The CERN Resonant WISP Search: Development, Results and Lesson-Learned|
|148||Dec. 13-14(Wed.-Thu.) 13:30 PM||자연과학동 대형강의실 (1501호)||장기주 교수 외 9명||KAIST-KIAS Joint Workshop in Theoretical Sciences 개최|
|147||Apr. 27, 2017 (Thu) 4:00 pm||Seminar Room(#1323, E6-2)||Prof.Donghan Lee (Chungnam National Univ.)||반도체 양자점을 이용한 단광자 광원|
|146||2017/03/06 - 05/29||Seminar Room 1501||이종봉 박사 (POSTECH) 외||Spring 2017: Physics Colloquium|
|145||2017/03/21 - 06/08||Seminar Room 1323||조길영 박사(KAIST) 외||Spring 2017: Physics Seminar Serises|
|144||Thursday, December 14, 2017 at 3:00 pm||Seminar Room (C303), Creation Hall (3F), KAIST Munji Campus||Chunglee Kim (KASI)||Exploring the Universe via GWs in the era of multi-messenger astronomy|
|143||Jun. 14 (Tue) 4PM||Seminar Room (#2502, 2nd fl.)||Young-Sik Ra, Université Pierre et Marie Curie||Photonic quantum network based on multimode squeezed vacuums and single-photon subtraction|
|142||Nov. 1 (Tue.) 2:30 pm||Seminar Room #1323(E6-2)||Prof. Youngjoon Kwon, Yonsei Univ.||Search for dark sector particles in the B-factory experiments|
|141||2015/06/03, 12PM||Room 101, E11||Prof. Min-Kyo, Seo & Hansuek, Lee(KAIST)||The First Wednesday Multidisciplinary Forum|
|140||April 5th 2017, 12:00 ~ 13:00||Room 101, Creative Learning Bldg.(E11)||Prof. Wonho Choe(Dept. of Physics),Prof. Young-chul GHIM(Dept. of Nuclear & Quantum Engineering)||2017년 4월 첫수 융합포럼 개최 안내(물리학과 & 원자력 및 양자공학과 공동 개최)/The First Wednesday Multidisciplinary Forum in April 2017 organized by Dept. of Physics & Dept. of Nuclear & Quantum Engineering|
|139||2016/09/05-12/12 4PM||Natual Scien Bldg.(E6)m #1501||Yeong Kwan Kim 외||Physics Colloquium : 2016 Fall|
|138||May 19, 2016 (Thur.) 3PM||May 19, 2016 (Thur.) 3PM,||Dr. Michael Betz, CERN||The CERN Resonant WISP Search: Development, Results and Lesson-Learned|
|137||2017.1.9(Mon), 4PM||Lecture Hall, College of Natural Sciences [#1501,E6-2]||Prof. John Michael Kosterlitz, Brown University||Topological Defects and Phase Transitions"|
|136||4월 18일(월), 15:30~||KI빌딩(E4), 강의실 B501 (5F)||Prof. Robert A. DiStasio Jr. (Cornell University)||First Principles Approaches for Intermolecular Interactions: From Gas-Phase Dimers to Liquid Water and Molecular Crystal Polymorphism|
|135||2014/05/28, PM5||KI Building, Matrix Hall||이웅범 대표이사(LG이노텍)||부품소재산업이 미래다|
|134||Aug. 4, 2016 (Thu.), 2:30 pm||KAIST Natural Science Building (E6-5), EDU 3.0 Room(1st fl.)||Prof. Argyris Nicolaidis||Relational Logic (with applications to Quantum Mechanics, String Theory, Cosmology, Neutrino Oscillations, Statistical Mechanics)|
|133||April 4, 2016 (Mon) - April 8, 2016 (Fri)||KAIST Natural Science Building (E6-2), RM #4314||Dr. Fritz Caspers (CERN)||Radio frequency engineering|
|132||2015/10/14, 6PM||KAIST Munji Campus Supex Hall||이창환 교수 (부산대학교 물리학과)||인터스텔라 영화 속의 물리|