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)
465 2016-11-01 14:30    Search for dark sector particles in the B-factory experiments
464 2017-04-06 16:00    For whom the Belle tolls
463 2024-07-23 16:00    Spin Conversion Research Towards Novel Spintronic Functionalities file
462 2020-12-23 10:00    Online workshop for Quantitative Phase Imaging file
461 2015-10-23 10:30    How to write a good scientific paper[Open lecture series]
460 2018-05-17 13:30    Quantum Spin Liquid in Kitaev Materials file
459 2023-07-12 11:00    Study of spin-1/2 antiferromagnetic kagome Heisenberg model by symmetric projected entangled simplex states
458 2017-09-12 16:00    Exact Solution for the Interacting Kitaev Chain at Symmetric Point file
457 2017-09-13 16:00    An Introduction to Quantum Spin Liquids file
456 2023-12-08 10:30    Novel transport phenomena in insulators
455 2017-11-08 13:00    “Emergent exotic quasiparticles in quantum spin liquids” file
454 2020-09-22 09:30    Physics and applications of soliton microcombs(Quantum- & Nano-Photonics) file
453 2017-04-05 12:00    2017년 4월 첫수 융합포럼 개최 안내(물리학과 & 원자력 및 양자공학과 공동 개최)/The First Wednesday Multidisciplinary Forum in April 2017 organized by Dept. of Physics & Dept. of Nuclear & Quantum Engineering file
452 2024-11-21 16:00  Prof. Ulrich Höfer  Time-resolved photoemission: From bandstructure to orbital movies file
451 2020-10-09 09:00    Quantum Many-Body Simulation file
450 2023-11-08 10:00    [High Energy Theory seminar] The Vacuum Sector of Asymptotically Isometric Codes
449 2018-05-31 16:00    Dynamic control of optical properties with gated-graphene metamaterials file
448 2023-05-17 16:30    Detecting Hidden Photon Dark Matter via the Excitation of Qubits file
447 2023-02-20 16:00    Physics of ferromagnet/superconductor junctions
446 2025-02-17 16:00  Prof. Takehito Yokoyama  Unconventional spin-spin interaction mediated by Cooper pairs or phonons file