visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나
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].

       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 [5]. 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 [6]. Dynamics being either within or beyond a simple two-temperature model scheme is observed in layered Dirac semimetals such as graphite and SrMnBi2 [7].

[1] Y. Ishida et al., Rev. Sci. Instrum. 85, 123904 (2014); Y. Ishida et al., Sci. Rep. 6, 18747 (2016). 

[3] P. Zhang et al., Phys. Rev. Lett. 118, 046802 (2017). 

[3] S. Kim et al., Phys. Rev. Lett. 112, 136802 (2014). 

[4] I. Belopolski et al., Nature Commun. 7, 13643 (2016). 

[5] Y. Ishida et al., Sci. Rep. 5, 8160 (2015); M. Neupane et al., Phys. Rev. Lett. 115, 116801 (2015).

[6] S. Zhu et al., Sci. Rep. 5, 13213 (2015). 

[7] Y. Ishida et al., Sci. Rep. 1, 64 (2011); Y. Ishida et al., Phys. Rev. B 93, 100302(R) (2016). 

 

번호 일시 장소 연사 제목
공지 2019/09/18 - 12/5  Seminar Room #1323  Prof. David Schuster and etc.  Fall 2019: Physics Seminar Serises
공지 2019/09/02 - 12/09  Seminar Room 1501  이호성 박사 (한국표준과학연구원) and etc.  Fall 2019: Physics Colloquium
90 2015/07/16, 4PM  E6-2, 1318  Dr. Kyunghan Hong(MIT)  Next-generation ultrafast laser technology for nonlinear optics and strong-field physics
89 November 1 (Thu.), 16:00 PM  #1323, E6-2  Dr. KyeoReh Lee  Direct holography from a single snapshot file
88 2016/03/11 1:30 PM  E6-2. 1st fl. #1501  Dr. Kwon Park  Topological phases of matter in nonequilibrium: Topology of the Wannier-Stark ladder
87 2015/12/11, 1:30PM  E6-2, #1323  Dr. KwangYong Choi  (Chung-Ang University)  Quantum spin liquid in the 1/3 depleted triangular lattice Ba3(Ru1-xIrx)Ti2O9
86 Dec. 9(Fri), 4p.m.  #1323(E6-2. 1st fl.  Dr. Kun Woo Kim, KIAS  Shift Charge and Spin Photocurrents in Dirac Surface States of Topological Insulator
85 May. 11 (Fri.), 02:30 PM  E6-2. 1st fl. #1323  Dr. Kun Woo Kim  Disordered Floquet topological insulators file
84 May 31 (Tue.) 4 PM  #1323(E6-2, 1st fl.)  Dr. Kimin Kim, KAIST  Understanding 3D tokamak physics towards advanced control of toroidal plasma
83 Apr. 01 (Fri.) 2:30 PM  E6-2. 1st fl. #1501  Dr. KICHEON KANG, Chonnam National University  Interference of single charged particles without a loop and dynamic nonlocality
82 Nov. 11th(Fri), 1:30 p.m.  #1323(E6-2. 1st fl.)  Dr. Keun Su Kim, POSTECH  Bandgap Engineering of Black Phosphorus
81 November 29 (Thu.), 16:00 PM  #1323, E6-2  Dr. Kee suk Hong  양자 칸델라 실현을 위한 단일 광자 발생장치 개발 file
80 2015/11/24, 4PM  E6-2, #1323  Dr. Kab-Jin Kim (Institute for Chemical Research, Kyoto University, Japan)  Topology-based understanding of spin dynamics in inhomogeneously magnetized systems
79 Jul. 08 (Fri.) 2PM  #1323(E6-2. 1st fl.)  Dr. Junhyun Lee, Harvard University  Electronic quasiparticles in the quantum dimer model
78 Oct. 18 (Tue.), 3PM  E6-2. 1st fl. #1323  Dr. JunHo Suh, Korea Research Institute of Standards and Science  “Hybrid quantum systems with mechanical oscillators”
77 2015/12/17, 11:00AM  E4(KI Building), Matrix Hall (2nd fl.)  Dr. Jung-Hoon Park (Purdue University)  Wavefront engineering for in-vivo Deep brain imaging
76 June 27 (Wed.), 13:30 PM  #1323, E6-2  Dr. Jung Sik Park  Magnetic reversal of artificial spin ice file
75 July. 14 (Fri.), 3:00 PM  #1323 (E6-2. 1st fl.)  Dr. Jun Hyun Lee / University of Maryland  Chiral anomaly in disordered Weyl semimetals file
74 Sep. 27 (Fri.), 02:30 PM  E6-2. 1st fl. #1323  Dr. Joon Sue Lee  Spin-charge conversion in topological insulators for spintronic applications file
73 Dec. 7 (Fri.), 04:00 PM  E6-2. 1st fl. #1323  Dr. Joon Ho Jang  Novel probes of interacting electrons in 2D systems file
72 October 19 (Fri.), 10:00 AM  #1323, E6-2  Dr. Jongsoo Yoo  Energy conversion processes during magnetic reconnection in a laboratory plasma file
71 Nov. 04 (Fri), 1:30 PM  E6-2. #1323(1st fl.)  Dr. Jonghyun Song, Department of Physics, Chungnam National University  Exotic phenomena at oxide LaAlO3/SrTiO3 hetero-interface and their applications