|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).
|218||Sep. 02(Fri) 4:00 PM||E6-2(1st fl) #1323||Dr. Yong-Joo Doh, Department of Physics and Photon Science, GIST||Quantum Electrical Transport in Topological Insulator Nanowires|
|217||October 15 (Mon.), 16:00 PM||#1323, E6-2||Dr. Yongjoo Baek||Universal properties of macroscopic current-carrying systems|
|216||April 11 (Wed), 1:30pm||#1323 (E6-2, 1st fl.)||Dr. Yongsoo Yang||Probing 3D Structure and Physical Properties of Materials at the Single-Atom Level|
|215||Jun. 10 (Fri.), 11:00 AM||Online seminar||Dr. Yoon Jang Chung(Laboratory for Physical Sciences, University of Maryland)||Record-quality two-dimensional electron systems|
|214||May. 13 (Fri.), 04:00 PM||자연과학동(E6-2) 1st fl. #1323||Dr. Yosep Kim(Center for Quantum Information, KIST)||High-fidelity iToffoli gate for fixed-frequency superconducting qubits|
|213||May. 12 (Fri.), 01:30 PM||E6-2. 1st fl. #1323||Dr. Young Kuk Kim||Topological Dirac insulator|
|212||April 11 (Wed), 4:00pm||#1323 (E6-2, 1st fl.)||Dr. Young-Sik Ra||Non-Gaussian states of multimode light generated via hybrid quantum information processing|
|211||May 13 (Fri.), 1:30 PM||E6. #1501(1st fl.)||Dr. Young-Woo Son, Dept. of Physics, KIAS||Aperiodic crystals in low dimensions|
|210||Aug. 9 (Tue), 14:00 PM||KI building (E4), Lecture Room Red (B501)||Dr. YoungChan Kim (Quantum Biophotonics Group, University of Surrey, UK)||Quantum biology in fluorescent protein: a new model system to study quantum effects in biology|
|209||Mar. 16 (Fri.), 04:0 PM||E6-2. 1st fl. #1323||Dr. YoungDuck Kim||Van der Waals Heterostructures from Quantum Transport to Ultrafast Optoelectronics|
|208||2015/11/06, 4:30 PM||E6-2, #5318||Dr. Youngkuk Kim (University of Pennsylvania)||Topological Dirac line nodes in centrosymmetric semimetals|
|207||Apr. 19 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. YoungWoo Nam||A family of finite-temperature electronic phase transitions in graphene multilayers|
|206||Nov. 1 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. YoungWook Kim||Squeezing the best out of 2D materials|
|»||Sep. 26 (Tue.), 11AM||#1323 (E6-2. 1st fl.)||Dr. Yukiaki Ishida / ISSP, University of Tokyo||Time-resolved ARPES study of Dirac and topological materials|
|204||Apr. 08 (Fri.), 13:30 PM||E6-2. 1st fl. #1501||Dr. Yunkyu Bang, Chonnam National Univ.||Theoretical Overview of Iron-based superconductors and its future|
|203||June 28 (Fri.), 13:30 PM||#1323, E6-2||Dr. Yusuke Kozuka||Magnetic domains and domain wall conduction in pyrochlore iridate thin films and heterostructures|
|202||Oct. 27th(Thu) 4PM||#1323(E6-2)||Dr. 이 강 희, KAIST, Mechnical Engineering||Terahertz Metal Optics|
|201||Nov. 18th (Fri) 10:30 a.m.||#5318(5th fl.)||Dr. 최 순 원, Havard University||Non-equilibrium many-body spin dynamics in diamond|
|200||May. 18(Wed), 4pm||E6-2. #1323 & Zoom||Dr.Heeyeon Kim (Rutgers University, Department of Physics and Astronomy)||Geometry, Algebra, and Quantum Field Theory|
|199||May. 19(Thu), 4pm||E6-2. #1323 & Zoom||Dr.Jay Hyun Jo (Yale University, Department of Physics)||Chasing Long Standing Neutrino Anomalies with MicroBooNE|