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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
235 Nov. 11th (Fri), 4 p.m.  #1323(E6-2. 1st fl.)  Dr. Bohm-Jung Yang, SNU  Dirac fermions in condensed matters
234 Nov. 16 (Wed), 4p.m.  #1323(E6-2. 1st fl.)  Dr. Heung-Sik Kim , University of Toronto  Realizing Haldane Model in Fe-based Honeycomb Ferromagnetic Insulators
233 Nov. 24(Thu) 4p.m.  #1323(E6-2. 1st fl.)  Dr. Jai-Min Choi, Chonbuk National Univiersity  Harmonic oscillator physics with single atoms in a state-selective optical potential
232 Nov. 29(Tue) 4p.m.  #1323(E6-2. 1st fl.)  Dr. SungBin Lee, KAIST  Symmetry Protected Kondo Metals and Their Phase Transitions
231 Dec. 8(Thu) 4p.m.  #1323(E6-2. 1st fl.)  Dr. Jinhyoung Lee, Hanyang University  Dynamical Resonance between Two Optical Cavities via Optomechanical Oscillator
230 Dec. 9(Fri), 1:30 p.m.  #1323(E6-2. 1st fl.)  Dr. Jae Yoon Cho, POSTECH  Entanglement area law in strongly-correlated systems
229 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
228 October 18 (Thu.), 16:00 PM  #1323, E6-2  Prof. Jongseok Lee  Applications of nonlinear optics for condensed matter researches file
227 October 4 (Thu.), 16:00 PM  #1323, E6-2  Prof. Soo Jin Kim  Engineering light absorption in an ultrathin semiconductor metafilm file
226 October 11 (Thu.), 16:00 PM  #1323, E6-2  Prof. Joung-Real Ahn  Dirac electrons in a graphene quasicrystal file
225 October 15 (Mon.), 16:00 PM  #1323, E6-2  Dr. Yongjoo Baek  Universal properties of macroscopic current-carrying systems file
224 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
223 October 18 (Thu.), 10:00 AM  #1323, E6-2  Dr. Duyoung Min  Understanding membrane protein folding using single-molecule force techniques file
222 October 19 (Fri.), 10:00 AM  #1323, E6-2  Dr. Jongsoo Yoo  Energy conversion processes during magnetic reconnection in a laboratory plasma file
221 September 5 (Wed.), 16:00 PM  #1323, E6-2  Dr. Dirk Wulferding  Shining a light on fractional excitations file
220 September 20 (Thu.), 16:00  #1323, E6-2  Prof. Joo-Hiuk Son  Toward Cancer Treatment Using Terahertz Radiation: Demethylation of Cancer DNA file
219 June 27 (Wed.), 13:30 PM  #1323, E6-2  Dr. Jung Sik Park  Magnetic reversal of artificial spin ice file
218 May 9 (Wed.), 04:00 PM  #1323, E6-2  Prof. Jong-Soo Rhyee  Recent advances in thermoelectric bulk composites file
217 May 29 (Tue.), 04:00 PM  #1323, E6-2  Prof. Jae-Won Jang  Investigation on metal nanostructure/semiconductor junction and its applications file