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
568 2024-11-21 16:00  자연동(E6) 1323호  Time-resolved photoemission: From bandstructure to orbital movies / Nanophotonics 초세대 협업 연구실 file
567 2024-11-13 12:00  Online  [11/13(수) 물리학과 세미나 안내] Separability as a window to mixed-state quantum phases and phase transitions / Tarun Grover (UC San Diego, Associate Professor)
566 2024-10-31 13:00  E6-2 / Rm. 3441  Mini-workshop on first-principles DFT methods and applications
565 2024-10-30 14:30  E6-2, #3441  [Seminar Invitation] Mario Cuoco (CNR-SPIN, c/o University of Salerno, Fisciano, Italy) / 2024.10.30. 14:30 / E6-2, #3441
564 2024-10-21 13:00  E6-2 #3441  [Physics Seminar] “Non-Hermitian Point-Gap Topology in Junction Systems” file
563 2024-10-17 16:00  온라인 (https://kaist.zoom.us/j/89289652931?pwd=eNz6xnTFrEMGXYj9fXpdBJsW9fEpJX.1)  Photonic Methods for Quantum Levitodynamics Beyond the Rayleigh Regime
562 2024-10-14 11:00  KI Building(E4), Matrix Hall(2nd Floor)  [RSVP, Oct 14th Mon] Ambassador of Hungary to Republic of Korea Special Lecture file
561 2024-10-02 12:00  E6-2, #3441  Data-driven discovery of neural computations through brain-wide and cell-type-specific dynamical systems file
560 2024-09-26 14:00  KAIST, Physics Bldg. (E6-2) / (Rm. 3441)  Quantum spin nematic phase in a square-lattice iridate
559 2024-09-03 12:00  자연과학동(E6-2) 1323  2024 가을학기 물리학과 특별세미나 전체 일정 (응집물리 및 광학분야) file
558 2024-09-02 16:00  자연과학동 1501호(공동강의실)  2024학년도 가을학기 물리학과 콜로키움(Physics Colloquium) file
557 2024-08-22 16:00  RM #C303, Creation Hall (3F), KAIST Munji Campus  [CAPP seminar] Development of a 12-20 GHz CO Intensity Mapping Receiver for Capturing the Star-formation History in the Early Universe file
556 2024-08-16 11:00  E6 1322 (no zoom broadcasting)  Cathodoluminescence for nanophotonics: Applications to plasmonic bandgap materials and perovskite semiconductors file
555 2024-08-14 11:00  E6, #3441  Pair Density Waves and Supercurrent Diode Effect in Altermagnets
554 2024-07-25 16:00  Rm. 3441, E6-2 (Advanced Physics Lecture Hall)  Generation and Certification of Optical Quantum States for Information Processing file
553 2024-07-23 16:00  KI Building(E4) Matrix Hall(2F)  Spin Conversion Research Towards Novel Spintronic Functionalities file
552 2024-07-22 14:00  E6-2 #3441  Nonthermal electronic orders in photo-doped Mott insulators
551 2024-07-18 11:00  E6-2 #1323  Acousto-electric non-local detection of magnon-phonon coupling
550 2024-07-10 16:00  E6-2 #2502  [High Energy Theory Seminar] The Weak Gravity Conjecture in Perturbative String Theory
549 2024-07-03 16:00  E6-2 #2502  [High Energy Theory Seminar] Holographic duals of Higgsed Dpb(BCD)