|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. 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 . 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 . Dynamics being either within or beyond a simple two-temperature model scheme is observed in layered Dirac semimetals such as graphite and SrMnBi2 .
 Y. Ishida et al., Rev. Sci. Instrum. 85, 123904 (2014); Y. Ishida et al., Sci. Rep. 6, 18747 (2016).
 P. Zhang et al., Phys. Rev. Lett. 118, 046802 (2017).
 S. Kim et al., Phys. Rev. Lett. 112, 136802 (2014).
 I. Belopolski et al., Nature Commun. 7, 13643 (2016).
 Y. Ishida et al., Sci. Rep. 5, 8160 (2015); M. Neupane et al., Phys. Rev. Lett. 115, 116801 (2015).
 S. Zhu et al., Sci. Rep. 5, 13213 (2015).
 Y. Ishida et al., Sci. Rep. 1, 64 (2011); Y. Ishida et al., Phys. Rev. B 93, 100302(R) (2016).
|공지||2019/09/18 - 12/5||Seminar Room #1323||Prof. David Schuster and etc.||Fall 2019: Physics Seminar Serises|
|공지||2019/09/02 - 12/09||Seminar Room 1501||이호성 박사 (한국표준과학연구원) and etc.||Fall 2019: Physics Colloquium|
|226||2015/09/14, 2PM||E6-2. 2nd fl. #2501||Dr. Hae Ja Lee ( Stanford University, SLAC )||Ultrafast X-ray Studies on Dynamics Matter in Extreme Conditions|
|225||Sep. 22, 2016(Thu), 3:30 PM||#1323(E6-2, 1st fl.)||Dr. Haiyang Yan (Institute of Nuclear Physics and Chemistry)||Polarized 3He, Polarized Neutrons and New Interactions beyond the Standard Model|
|224||Sep. 22, 2016(Thu), 3:30 PM||#1323(E6-2, 1st fl.)||Dr. Haiyang Yan (Institute of Nuclear Physics and Chemistry)||Polarized 3He, Polarized Neutrons and New Interactions beyond the Standard Model|
|223||May 19 (Thu) 4PM||#1323(E6-2, 1st fl.)||Dr. Heedeuk Shin, POSTECH||Nonlinear/quantum optical effect in silicon nano-photonics|
|222||2015/10/23, 3PM||E6-2, #5318||Dr. Helmut Soltner (Forschungszentrum Juelich)||Development of a Rogowski Coil as a new beam position monitor|
|221||Jun 24 (Mon) 11:00||E6-2, #1323||Dr. Henning Schomerus||Topological photonic anomalies|
|220||4pm, Sep. 21 (Wed.||E6-2. #2502(2nd fl.)||Dr. Henrik Johannesson , University of Gothenburg (Sweden) and Beijing Computational Science Research Center (China)||Entanglement probe of two-impurity Kondo physics|
|219||Jan.9 (Wed.), 04:00 PM||E6-2. 2nd fl. #2501||Dr. Heung-Sik Kim||Molecular Mott state in the deficient spinel GaV4S8|
|218||Nov. 16 (Wed), 4p.m.||#1323(E6-2. 1st fl.)||Dr. Heung-Sik Kim , University of Toronto||Realizing Haldane Model in Fe-based Honeycomb Ferromagnetic Insulators|
|217||May 13 (Fri.) 4 PM||E6. #1501(1st fl.)||Dr. Hosub Jin, Dept. of Physics, UNIST||Graphene analogue in (111)- BaBiO3 bilayer heterostructures for topological electronics|
|216||July 27, 2018 at 15:00||Room 5318, KAIST Natural Sciences Lecture Hall(E6).||Dr. Hyejung Kim(Technische University Dresden)||Muon g-2 in the 2HDM and MSSM: comprehensive numerical analysis and absolute maxima|
|215||Oct. 12 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. HyungWoo Lee||Direct observation of a two-dimensional hole gas at oxide interfaces|
|214||Dec. 26 (Wed.), 04:00 PM||E6-2. 1st fl. #1323||Dr. Isaac H. Kim||Brane-like defect in 3D toric code|
|213||July 31(Wed.)/ 16:00||E6-2, #1323||Dr. Ivan Borzenets||Features of ballistic superconducting graphene|
|212||Thursday, July 12, 2018 at 17:00||Room 5318, KAIST Natural Sciences Lecture Hall(E6)||Dr. Jae Hyeok Yoo (University of California, Santa Barbara, Department of Physics)||The MilliQan Experiment: Search for Milli-Charged Particles at the LHC|
|211||Dec. 9(Fri), 1:30 p.m.||#1323(E6-2. 1st fl.)||Dr. Jae Yoon Cho, POSTECH||Entanglement area law in strongly-correlated systems|
|210||October 16 (Wed), 4:00pm||#1323 (E6-2, 1st fl.)||Dr. Jaewon Song||Emergent black holes and monopoles from quantum fields|
|209||Nov. 24(Thu) 4p.m.||#1323(E6-2. 1st fl.)||Dr. Jai-Min Choi, Chonbuk National Univiersity||Harmonic oscillator physics with single atoms in a state-selective optical potential|
|208||2015/09/07, 3PM||E6-2. 1st fl. #1318||Dr. Jasbinder Sanghera (U.S. Naval Research Laboratory (NRL))||Advanced Optical Materials and Devices at NRL|
|207||Apr. 12 (Tue.), 4 PM||E6-2. 1st fl. #1323||Dr. Jeehoon Kim, POSTECH||Confinement of Superconducting Vortices in Magnetic Force Microscopy|