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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
130 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 file
129 February 21 (Thu.), 16:00 PM  #5313, E6-2  Prof. Diptimoy Ghosh  B-meson charged current anomalies - Theoretical status file
128 Feb. 25 - Jun 3  Rm. 1501 (E6)    Spring 2019: Physics Colloquium file
127 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
126 Feb. 1 (Wed.), 2p.m.  #1323(E6-2. 1st fl.)  Dr. Michihisa Yamamoto, Department of Applied Physics, The University of Tokyo  Quantum electron optics using flying electrons
125 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
124 Dec. 9(Fri), 1:30 p.m.  #1323(E6-2. 1st fl.)  Dr. Jae Yoon Cho, POSTECH  Entanglement area law in strongly-correlated systems
123 Dec. 8(Thu) 4p.m.  #1323(E6-2. 1st fl.)  Dr. Jinhyoung Lee, Hanyang University  Dynamical Resonance between Two Optical Cavities via Optomechanical Oscillator
122 Dec. 7 (Fri.), 04:00 PM  E6-2. 1st fl. #1323  Dr. Joon Ho Jang  Novel probes of interacting electrons in 2D systems file
121 Dec. 7 (Fri.), 02:30 PM  E6-2. 1st fl. #1323  Dr. Gyung Min Choi  Spin generation from heat and light in metals file
120 DEC. 27 (Thu), 04:00 PM  E6-2. 1st fl. #1323  Prof. Na Young Kim  Quantum Innovation (QuIN) Laboratory file
119 Dec. 26 (Wed.), 04:00 PM  E6-2. 1st fl. #1323  Dr. Isaac H. Kim  Brane-like defect in 3D toric code file
118 DEC. 26 (Wed), 04:00 PM  E6-1. 3rd fl. #3434  Y. Kim, A. Go, K. Hwang and E.-G. Moon  Informal Workshop on Topology and Correlation file
117 DEC. 16~18 (Sun~Tue)  E6-2. 1st fl. #1323  Prof. Keisuke Totsuka  Lectures on 2d Conformal Field Theory file
116 Dec. 15 (Fri.), 9:20 AM  E6-2, Lecture Room #1323  Prof. Jhinhwan Lee 외 9명  Workshop on Magnetism in Unconventional Superconductors 개최 file
115 Dec. 13-14(Wed.-Thu.) 13:30 PM  자연과학동 대형강의실 (1501호)  장기주 교수 외 9명  KAIST-KIAS Joint Workshop in Theoretical Sciences 개최 file
114 Dec. 12th (Mon)  1:30p.m. #1323(E6-2. 1st fl.)  Dongjoon Song , AIST  “Possible symmetry in the phase diagrams of electron- & hole-doped cuprate high-Tc superconductors”
113 DEC. 11 (Tue), 04:00 PM  E6-2. 1st fl. #1323  Prof. Hiroshi Shinaoka  Natural compact representation of Matsubara Green’s functions: applications to analytic continuation and quantum many-body simulations file
112 August. 6th (TUE), 14:00  E6 Room(#1323)  Kanghyun Chu  Visualization of in-plane piezoresponse vector fields file
111 August. 1st (Thu), 14:00  E6 Room(#1323)  Hyeok Yoon  Low-density Superconductivity in SrTiO3 Probed by Planar Tunneling Spectroscopy file