visual
visual

세미나

  • 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
222 2023-03-22 16:00  E6-2, #2502  (High Energy Theory Seminar) Boltzmann or Bogoliubov? A Case of Gravitational Particle Production
221 2023-11-22 16:00  E6-2, #2502  [High Energy Theory Seminar] Renormalization and the Hierarchy Problem
220 2023-10-04 16:00  E6-2, #2502  [High-Energy Theory Seminar] Moving towards quantum technologies: the case of quantum batteries
219 2023-05-03 16:00  E6-2, #2502  Probing microscopic origins of axions by the chiral magnetic effect
218 2023-09-26 16:00  E6-2, #2502  [High Energy Theory Seminar]A new step in interacting dark sector cosmologies
217 2023-06-14 16:00  E6-2, #2502  [High-Energy Theory Seminar]Vertex algebras and extended operators in 4d N=2 SCFTs
216 2023-06-16 13:00  E6-2, #2502  Quantum critical states under extreme conditions
215 2023-11-01 16:00  E6-2, #2502  [High Energy Theory Seminar] Modular functions and 3D N=4 rank-zero superconformal field theories
214 2023-08-29 16:00  E6-2, #2502  [High Energy Theory Seminar] Towards string loop corrections in Calabi-Yau orientifold compactifications.
213 2023-06-01 16:00  E6-2, #5301  Hall viscosity and topological phenomena
212 2023-11-22 10:00  E6-2, #5301 & zoom  [High Energy Theory Seminar] Exact Quantum Algorithms to Recognize Quantum Phases of Matter
211 2020-02-12 13:00  E6-2, #5318  From inflation to new weak-scale file
210 2015-11-06 16:30  E6-2, #5318  Topological Dirac line nodes in centrosymmetric semimetals
209 2015-10-23 15:00  E6-2, #5318  Development of a Rogowski Coil as a new beam position monitor
208 2015-07-16 16:00  E6-2, 1318  Next-generation ultrafast laser technology for nonlinear optics and strong-field physics
207 2015-07-16 16:00  E6-2, 1501  KAIST Physics Distinguished Lecture
206 2016-03-11 13:30  E6-2, 1501 외  Physics Seminar Serises : 2016 Spring file
205 2019-07-03 15:00  E6-2, 2501  Many-body quantum electrodynamis (QED) with atoms and photons: A new platform for quantum optics" file
204 2018-06-14 10:00  E6-2, 2nd fl. #2502  Phonons and polariton-like particles in trapped ions for quantum computation and quantum simulation file
203 2015-10-16 15:00  E6-2, 5th fl. #5318  High Magnetic Fields to Probe the sub-eV range of Particle/Astroparticle Physics - From the OSQAR experiments at CERN up to new perspectives at LNCMI-Grenoble