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장소 #1323 (E6-2. 1st fl.) 
일시 Sep. 26 (Tue.), 11AM 
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 일시 장소 연사 제목
공지 2018/03/27 - 06/07  Seminar Room #1323  김성곤 교수(Mississippi State Univ.) and etc.  Spring 2018: Physics Seminar Serises
공지 2018/03/05 - 06/04  Seminar Room 1501  정수영 박사 (KIST) and etc.  Spring 2018: Physics Colloquium
157 2010/02/14-05/09  E6, 1501  황철주(주성엔지니어링 사장) 외  Physics Colloquium - 2011 Spring file
156 2015/03/09-06/08  E6, 1501  최현용교수(연세대) 외12명  Physics Colloquium : 2015 Spring file
155 2010/02/08-05/03  E6, 1501  최인수교수(서울대) 외  Physics Ciolloquium : 2010 Spring file
154 2009/10/21, 4PM  E6, 1501  최석봉교수(서울대)  Interdimensional Universality of Dynamic Interfaces
153 2010/09/06-12/06  E6, 1501  조호진기자(조선일보) 외  Physics Colloquium : 2010 Fall file
152 2017/03/21 - 06/08  Seminar Room 1323  조길영 박사(KAIST) 외  Spring 2017: Physics Seminar Serises file
151 Dec. 13-14(Wed.-Thu.) 13:30 PM  자연과학동 대형강의실 (1501호)  장기주 교수 외 9명  KAIST-KIAS Joint Workshop in Theoretical Sciences 개최 file
150 2015/10/14, 6PM  KAIST Munji Campus Supex Hall  이창환 교수 (부산대학교 물리학과)  인터스텔라 영화 속의 물리 file
149 2009/09/07-11/30  E6, 1501  이주영박사(KIAS) 외  Physics Colloquium : 2009 Fall file
148 2017/03/06 - 05/29  Seminar Room 1501  이종봉 박사 (POSTECH) 외  Spring 2017: Physics Colloquium file
147 2014/05/28, PM5  KI Building, Matrix Hall  이웅범 대표이사(LG이노텍)  부품소재산업이 미래다
146 2009/02/23-05/04  E6, 1501  안종현교수(성균관대) 외  Physics Colloquium : 2009 Spring file
145 2014/03/10-06/09  E6, 1501  신용일교수(서울대)  Physics Colloquium : 2014 Spring file
144 2011/05/16, 4PM  E6, 1501  서민교교수(KAIST)  Photonics with surface plasmon polaritons
143 5월 17일(화), 11:00 ~ 12:00  창의학습관(E11), 406호  방준혁 박사(Korea Basic Science Institute, KBSI)  The CERN Resonant WISP Search: Development, Results and Lesson-Learned
142 2013/09/09-12/09  E6, 1501  박혁규교수(부산대) 외  Physics Colloquium : 2013 Fall
141 April 6 (Fri.), 10:00 AM  #2502, E6  박채연 박사  Entanglement and thermalization in many-body systems: recent progress file
140 2015/09/15-12/08  E6, 1501  박제근 교수(서울대 물리학과) 외12명  Physics Colloquium : 2014 Fall file
139 2016/03/11-06/09  E6-2, 1501 외  박권(KAIS) 외  Physics Seminar Serises : 2016 Spring file