|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).
|228||Dec.9(Wed), 10:00AM||Zoom||Prof. Andrew Geraci (Northwestern University)||Searching for the QCD axion with the ARIADNE experiment|
|227||8/19 (Mon), 10:00~11:30, 8/22 (Thur), 10:00~11:30||Rm. 1322, E6-2||Nicolas Treps||Tutorials on Multimode Quantum Optics in the Continuous Variable Regime|
|226||Oct. 17th (Mon) 11:00 AM||#1323,(E6-2, 1st fl.)||Nguyen Quang Liem, Institute of Materials Science, VAST, Viettnam||IMS and examples of the studies on optoelectronic materials|
|225||Nov.26(Thu), 04:00PM||Online(Zoom)||Myung-Ki Kim||2020 가을학기 광학분야 특별세미나(Light Engineering Beyond the Diffraction Limit)|
|224||Dec. 11 (Fri.), 02:30 PM||online||Myung Hwa Jung(Sogang Univ.)||Antisymmetric interlayer exchange coupling in magnetic multilayers|
|223||Apr. 13(Wed.) 10:30Am||E6 #1323/zoom||Mingu Kang (Max Planck POSTECH Korea Research Initiative)||Harnessing topology and correlations from singularities in 3d-kagome metals|
|222||January 23, 2019||Rm. C303, Creation Hall (3F), Munji Campus||Mikko Mottonen||Ultrasensitive Microwave Bolometer: Opportunity for Axion Detectors|
|221||Aug, 25(Tue), 20:00~||Zoom webinar||Mark D. Stiles (NIST, USA)||KAIST Global Forum for Spin and Beyond (Second Forum)|
|220||Aug. 17(Mon), 20:00~||Zoom webinar||Mark D. Stiles (NIST, USA)||Using magnetic tunnel junctions to compute like the brain|
|219||July 26, 2018 at 14:00||Room 5318, KAIST Natural Sciences Lecture Hall(E6).||Manki Kim (Department of Physics, Cornell University)||Inflation in String Theory and Backreaction|
|218||Jul 3rd, 2019 (Wed)||E6-2, 2501||Kyung Soo Choi||Many-body quantum electrodynamis (QED) with atoms and photons: A new platform for quantum optics"|
|217||Jun 1 (Wed) 4 PM||#1323(E6-2 1st fl.)||Kil-Byoung Chai, Caltech||Laboratory experiments relevant to mesospheric clouds, Saturn’s rings & astrophysical jets|
|216||2012/02/13-05/14||E6, 1501||Kenji Ohmori (Photo-Molecular Science, IMS)||Physics Colloquium : 2012 Spring|
|215||August. 6th (TUE), 14:00||E6 Room(#1323)||Kanghyun Chu||Visualization of in-plane piezoresponse vector fields|
|214||July 21 - August 2||E6-2,# 5318||Junmou Chen/Thomas Flacke/Kaoru Hagiwara/Junichi Kanzaki/Chris Kelso/Jeong Han Kim/Kyoungchul Kong/Gabriel Lee/Hye-Sung Lee/Ian Lewis||Challenges and Opportunities in Theoretical Particle Physics 2019|
|213||Jan. 25th (Tue), 15:00||E6 #1501/online||Junhyun Lee (Rutgers, the State University of New Jersey)||Emulating twisted double bilayer graphene with a multiorbital optical lattice|
|212||Sep10(Tue), 15:00||#2502, E6-2||Jun Ho Son||(2+1) D Duality Web from 3D Euclidean Lattice|
|211||Jan 12th (Wed), 11:00 AM||Zoom and E6 #1323||Joonseok Hur (MIT)||Spectroscopic study of trapped ions towards probing dark matter and new physics|
|210||3pm, 19th May||online||Jonghee Yoon, PhD (Assistant professor, Department of Physics, Ajou University)||(광학분야 특별세미나)Development of a multimodal optical system for improved disease diagnosis|
|209||3pm, 19th May||online||Jonghee Yoon, PhD (Assistant professor, Department of Physics, Ajou University)||(광학분야 특별세미나)Development of a multimodal optical system for improved disease diagnosis|