visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나
날짜 2017-09-26 11:00 
연사  
장소 #1323 (E6-2. 1st fl.) 

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 연사 제목
공지 2025-02-24 16:00    2025년 봄학기 콜로키움 안내
공지 2025-02-27 16:00    2025년 봄 물리학과 특별세미나 (광학/응집물리 분야)
365 2023-06-08 16:00    Thermal decoupling in high-Tc cuprate superconductors
364 2019-05-31 11:00    Cavity QED with Spin Qubits file
363 2022-05-27 11:00    Current Status and Future Plans of ADMX file
362 2015-07-23 13:30    Enhanced ZnO based UV photonics and related applications file
361 2020-10-15 16:00    Graphene-based Josephson junction microwave bolometer file
360 2022-06-03 11:00    (응집물리 세미나) Theoretical Investigation of Exotic Quantum States in Low-dimensional Materials
359 2025-06-26 16:00  Prof. Eun-Ah Kim (Cornell)  Attention to Quantum Complexity file
358 2023-03-27 15:00    A coherent mechanical oscillator pumped by a suspended quantum dot file
357 2022-09-21 16:00    Materials and Device Nanofabrication of Optical Metasurfaces file
356 2023-11-01 16:00    [High Energy Theory Seminar] Modular functions and 3D N=4 rank-zero superconformal field theories
355 2019-02-21 16:00    B-meson charged current anomalies - Theoretical status file
354 2023-03-30 16:00    Detecting axions with chiral magnetic effects file
353 2019-09-18 16:00    Fall 2019: Physics Seminar Serises file
352 2016-03-07 16:00    Physics Colloquium : 2016 Spring file
351 2023-11-15 16:00    Quantum hydrodynamic theory for plasmonics: from molecule-coupling to nonlinear optics
350 2022-10-04 16:00    Distinguishing 6d (1, 0) SCFTs
349 2015-03-04 12:00    Bioimaging and Biosensing Using Near-Infrared Fluorescence file
348 2019-05-03 11:00    Exotic Magnetism file
347 2014-12-22 14:00    Dynamics of molecular motors: Power stroke vs Brownian ratchet file
346 2019-05-30 16:00    Tuning the excitonic properties of semiconductors with light-matter interactions file