|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|
|185||2015/07/16, 4PM||E6-2, 1318||Dr. Kyunghan Hong(MIT)||Next-generation ultrafast laser technology for nonlinear optics and strong-field physics|
|184||February 12(Web.)||E6-2, #5318||Prof. Kunio Kaneta||From inflation to new weak-scale|
|183||2015/11/06, 4:30 PM||E6-2, #5318||Dr. Youngkuk Kim (University of Pennsylvania)||Topological Dirac line nodes in centrosymmetric semimetals|
|182||2015/10/23, 3PM||E6-2, #5318||Dr. Helmut Soltner (Forschungszentrum Juelich)||Development of a Rogowski Coil as a new beam position monitor|
|181||2015/08/03,10:30AM||E6-2, #1323 (Seminar Room)||Dr. Jonghee Yoo (Fermi National Accelerator Laboratory, USA )||Axion Search|
|180||July 31(Wed.)/ 16:00||E6-2, #1323||Dr. Ivan Borzenets||Features of ballistic superconducting graphene|
|179||Jun 24 (Mon) 11:00||E6-2, #1323||Dr. Henning Schomerus||Topological photonic anomalies|
|178||July 25(Thur.),4:00PM||E6-2, #1323||Prof.Bohm-Jung Yang||Band topology of twisted bilayer graphene|
|177||2015/12/11, 3:45PM||E6-2, #1323||Dr. Ji Hun Sim (POSTECH)||Dynamical mean field theory studies on heavy fermion system|
|176||2015/11/10, 4PM||E6-2, #1323||Dr. Woosuk Bang (Physics division, Los Alamos National Laboratory)||Rapid heating of matter using high power lasers|
|175||2015/11/19, 4PM||E6-2, #1323||Dr. Daesu Lee (University of Wisconsin-Madison)||Emergent Collective Phenomena and Functions at Reduced Dimensions|
|174||2015/12/11, 1:30PM||E6-2, #1323||Dr. KwangYong Choi (Chung-Ang University)||Quantum spin liquid in the 1/3 depleted triangular lattice Ba3(Ru1-xIrx)Ti2O9|
|173||2015/12/03, 4PM||E6-2, #1323||Dr. Sang-Yun Lee (3rd institute of Physics, University of Stuttgart, Germany)||Hybrid solid state spin qubits in wide bandgap semiconductors|
|172||2015/11/28, 10AM||E6-2, #1323||Dr. Suyong Jung (Korea Research Institute of Standards and Science)||Electron Tunneling Spectroscopy of Single and Bilayer Graphene with Hexagonal Boron Nitride as Tunneling Barrier|
|171||2015/11/23, 1:30PM||E6-2, #1323||Dr. Michael Park (Stanford University)||What's Beyond the Standard Model? Lessons from Run I and what might come in Run II|
|170||2015/11/24, 4PM||E6-2, #1323||Dr. Kab-Jin Kim (Institute for Chemical Research, Kyoto University, Japan)||Topology-based understanding of spin dynamics in inhomogeneously magnetized systems|
|169||2016/1/11, 4PM||E6-2, #1323||Dr. B.J.Kim (Max Planck Institute for Solid State Research)||Mott Physics in the Strong Spin-Orbit Coupling Regime|
|168||2015/12/09, 2PM||E6-2, #1323||Arjun G. Yodh (University of Pennsylvania)||SWELLABLE COLLOIDAL PARTICLES ARE SWELL|
|167||2016/09/29-12/13||E6-2, #1323||Sangyoon Han 외||2016 Fall, Physics Seminar Serises|
|166||2015/12/02, 4PM||E6-2, #1323||Dr. Dae-Jeong Kim (Dept. of Physics and Astronomy, University of California, Irvine)||Samarium Hexaboride: Is it a Topological insulator?|