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 2019/03/21 - 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
137 April 13 (Fri.), 10am  #1323 (E6-2, 1st fl.)  Dr. Sungkun Hong  Quantum meets Mechanics: from Quantum Information to Fundamental Research file
136 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 file
135 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
134 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
133 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 file
132 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 file
131 October 16 (Tue.), 10:00 AM  #1323, E6-2  Dr. Won-Ki Cho  Capturing protein cluster dynamics and gene expression output in live cells file
130 2015/11/10, 4PM  E6-2, #1323  Dr. Woosuk Bang (Physics division, Los Alamos National Laboratory)  Rapid heating of matter using high power lasers
129 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
128 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
127 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
126 October 15 (Mon.), 16:00 PM  #1323, E6-2  Dr. Yongjoo Baek  Universal properties of macroscopic current-carrying systems file
125 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 file
124 May. 12 (Fri.), 01:30 PM  E6-2. 1st fl. #1323  Dr. Young Kuk Kim  Topological Dirac insulator
123 April 11 (Wed), 4:00pm  #1323 (E6-2, 1st fl.)  Dr. Young-Sik Ra  Non-Gaussian states of multimode light generated via hybrid quantum information processing file
122 May 13 (Fri.), 1:30 PM  E6. #1501(1st fl.)  Dr. Young-Woo Son, Dept. of Physics, KIAS  Aperiodic crystals in low dimensions
121 Mar. 16 (Fri.), 04:0 PM  E6-2. 1st fl. #1323  Dr. YoungDuck Kim  Van der Waals Heterostructures from Quantum Transport to Ultrafast Optoelectronics file
120 2015/11/06, 4:30 PM  E6-2, #5318  Dr. Youngkuk Kim (University of Pennsylvania)  Topological Dirac line nodes in centrosymmetric semimetals
119 Apr. 19 (Fri.), 02:30 PM  E6-2. 1st fl. #1323  Dr. YoungWoo Nam  A family of finite-temperature electronic phase transitions in graphene multilayers file
» Sep. 26 (Tue.), 11AM  #1323 (E6-2. 1st fl.)  Dr. Yukiaki Ishida / ISSP, University of Tokyo  Time-resolved ARPES study of Dirac and topological materials