• HOME
  • >
  • 소식
  • >
  • 세미나
날짜 2017-09-26 11:00 
일시 Sep. 26 (Tue.), 11AM 
장소 #1323 (E6-2. 1st fl.) 
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 날짜 장소 제목
515 2023-12-08 10:30  E6-2, Rm#2502  Novel transport phenomena in insulators new
514 2023-11-30 10:30  E6-2, #1322  [High-Energy Theory Seminar] 3d-3d correspondence and 2d N = (0,2) boundary conditions
513 2023-11-29 10:00  Zoom  [High Energy Theory Seminar] Averaged null energy and the renormalization group
512 2023-11-23 16:00  E6-2(Natural Science B/D). 1st fl. #1323  Deciphering the Enigma of Quantum Materials by X-ray Scattering and Spectroscopy
511 2023-11-22 16:00  E6-2, #2502  [High Energy Theory Seminar] Renormalization and the Hierarchy Problem
510 2023-11-22 10:00  E6-2, #5301 & zoom  [High Energy Theory Seminar] Exact Quantum Algorithms to Recognize Quantum Phases of Matter
509 2023-11-16 16:00  E6-2(Natural Science B/D). 1st fl. #1323  Electric-field control of emergent phenomena in correlated oxide thin films
508 2023-11-15 16:00  E6-6, #119  Quantum hydrodynamic theory for plasmonics: from molecule-coupling to nonlinear optics
507 2023-11-09 16:00  E6-2(Natural Science B/D). 1st fl. #1323  Assessing the Capability of Near-Term Photonic Devices Towards Quantum Supremacy
506 2023-11-08 10:00  E6-2,#2502 & zoom  [High Energy Theory seminar] The Vacuum Sector of Asymptotically Isometric Codes
505 2023-11-01 16:00  E6-2, #2502  [High Energy Theory Seminar] Modular functions and 3D N=4 rank-zero superconformal field theories
504 2023-10-19 11:00  E6-2 #1322  Emergent functionalities of iridium oxide films with different growth orientation file
503 2023-10-11 16:00  CAPP Seminar Room C303, Creation Hall, KAIST Munji Campus  [CAPP seminar] Particle Physics with Neutrinos file
502 2023-10-11 16:00  E6-2, Rm2502  [High Energy Theory Seminar] Axion Magnetic Resonance
501 2023-10-04 16:00  E6-2, #2502  [High-Energy Theory Seminar] Moving towards quantum technologies: the case of quantum batteries
500 2023-09-27 16:00  E6, Rm#2501  Chiral Magnets: Domain-Wall Skyrmions and String Theory Realization
499 2023-09-26 16:00  E6-2, #2502  [High Energy Theory Seminar]A new step in interacting dark sector cosmologies
498 2023-09-21 16:00  CAPP Seminar Room C303, Creation Hall, KAIST Munji Campus  [CAPP seminar] Axion Magnetic Resonance file
497 2023-09-18 16:00  CAPP Seminar Room C303, Creation Hall, KAIST Munji Campus  [CAPP Seminar] Searching for axions in quantum vacuum birefringence file
496 2023-09-18 11:00  E6-2, #1322  Magic polarisation trapping of polar molecules for tunable dipolar interactions file