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)
455 2018-05-17 13:30    Quantum Spin Liquid in Kitaev Materials file
454 2018-05-29 16:00    Investigation on metal nanostructure/semiconductor junction and its applications file
453 2018-05-31 16:00    Dynamic control of optical properties with gated-graphene metamaterials file
452 2018-06-01 11:00    Topological phases in low-dimensional quantum materials file
451 2018-06-14 10:00    Phonons and polariton-like particles in trapped ions for quantum computation and quantum simulation file
450 2018-06-18 10:00    Rydberg electromagnetically induced transparency and microwave-to-optical conversion using Rydberg atoms file
449 2018-06-22 10:00    Success in Research Career file
448 2018-06-22 16:00    Tuning functional properties of BiFeO3 films using strain and growth chemistry file
447 2018-07-02 15:00    High Precision Magnetic Field Measurement for the Muon g-2 Experiment file
446 2018-07-09 14:00    The principles of collective learning file
445 2018-07-12 17:00    The MilliQan Experiment: Search for Milli-Charged Particles at the LHC
444 2018-07-13 14:00    Loop Induced Single Top Partner Production and Decay at the LHC
443 2018-07-26 14:00    Inflation in String Theory and Backreaction file
442 2018-07-27 13:30    Magnetic reversal of artificial spin ice file
441 2018-07-27 15:00    Muon g-2 in the 2HDM and MSSM: comprehensive numerical analysis and absolute maxima file
440 2018-08-01 11:00    Future of AI: Is the brain a computer? file
439 2018-09-04 14:30    Ultrafast time- and angle-resolved photoemission spectroscopy (tr-ARPES) with extreme ultraviolet laser pulses file
438 2018-09-05 16:00    Shining a light on fractional excitations file
437 2018-09-07 15:00    Recent developments in density functional theory: From new functionals to the nature of the chemical bond file
436 2018-09-20 16:00    Toward Cancer Treatment Using Terahertz Radiation: Demethylation of Cancer DNA file