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
562 2009-02-23 16:00  E6, 1501  Physics Colloquium : 2009 Spring file
561 2009-09-07 16:00  E6, 1501  Physics Colloquium : 2009 Fall file
560 2009-10-21 16:00  E6, 1501  Interdimensional Universality of Dynamic Interfaces
559 2010-02-08 16:00  E6, 1501  Physics Ciolloquium : 2010 Spring file
558 2010-02-14 16:00  E6, 1501  Physics Colloquium - 2011 Spring file
557 2010-09-06 16:00  E6, 1501  Physics Colloquium : 2010 Fall file
556 2011-05-16 16:00  E6, 1501  Photonics with surface plasmon polaritons
555 2011-09-03 16:00  E6, 1501  Physics Colloquium : 2011 Fall file
554 2012-02-13 16:00  E6, 1501  Physics Colloquium : 2012 Spring
553 2012-04-02 16:00  E6, 1501  A new route to ferroelectricity in magnetic spinels: a case of Co2MnO4
552 2013-03-11 16:00  E6, 1501  Physics Colloquium : 2013 Spring
551 2013-09-09 16:00  E6, 1501  Physics Colloquium : 2013 Fall
550 2014-03-10 16:00  E6, 1501  Physics Colloquium : 2014 Spring file
549 2014-05-28 17:00  KI Building, Matrix Hall  부품소재산업이 미래다
548 2014-12-22 14:00  E6, Rm1319  Dynamics of molecular motors: Power stroke vs Brownian ratchet file
547 2015-03-04 12:00  1323호, E6-2  Bioimaging and Biosensing Using Near-Infrared Fluorescence file
546 2015-03-09 16:00  E6, 1501  Physics Colloquium : 2015 Spring file
545 2015-03-13 14:00  Connect Room, KI Bldg.  The 15th Innovative Workshop on Soft/Bio Materials file
544 2015-06-03 12:00  Room 101, E11  The First Wednesday Multidisciplinary Forum file
543 2015-07-15 14:00  E6-2,1323  Electronic and optical properties of titanate-based oxide superlattices