visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나
장소 #5318(E6-2. 5th fl.) 
일시 AUG. 31 (Thu.), 2 PM 
연사 Prof. Hiroaki Ishizuka (The University of Tokyo) 

“Berry phase and nonlinear response: photocurrent in noncentrosymmetric insulators and Weyl semimetals”

Prof. Hiroaki Ishizuka (The University of Tokyo)

AUG. 31 (Thu.), 2 PM / #5318(E6-2. 5th fl.)

 

Berry phase is one of the important keywords to understand non-trivial quantum effects. In condensed matter physics, the Berry phase often shows up in transport phenomena (e.g., quantum and anomalous Hall effects) and is considered as a keyword to understand topological properties of non-interacting fermion systems. While most of such studies have focused on the equilibrium states or linear responses in close to the equilibrium, a recent study on the photogalvanic effects have pointed out the relation between the Berry phase and photogalvanic effects in noncentrosymmetric insulators where inter-band transitions take an essential role [1-3]; it is named shift current as it is related to the shift of the Wannier function. So far, however, no observable consequences that distinguish this phenomenon from the conventional mechanism is known. In this talk, we theoretically explored the basic properties of shift current focusing on the distinction between the conventional and shift current mechanisms. 

To theoretically study the photocurrent, we employed a Keldysh Green’s function formalism combined with Floquet theory. Using a large size numerical calculation, we study how the photocurrent changes by the local excitation, i.e., when only a part of the system is irradiated by the light. We show that, for the shift current, the magnitude of the current does not depend on the position of the light [4]. This is in contrast to the conventional mechanism, where the photocurrent is expected to be larger at the edge of the sample while it is suppressed when the light is at the center. Such behavior is consistent with the photocurrent recently observed in a noncentrosymmetric organic solid [5].

In the latter half of the talk, we discuss the effect of Berry phase on the photocurrent in Weyl semimetals [6,7]. We show that the Berry phase associated with the Weyl nodes induce a similar phenomenon to the adiabatic pump, resulting in a dissipation-less photocurrent. We find that the photocurrent appears only with the circularly polarized lights. This mechanism may potentially explain the photocurrent observed in TaAs [8].

 

[1] W. Kraut and R. von Blatz, Phys. Rev. B 19, 1548 (1979); ibid. 23, 5590 (1981). 

[2] J. E. Sipe and A. I. Shkrebtii, Phys. Rev. B 61, 5337 (2000).

[3] T. Morimoto and N. Nagaosa, Science Adv. 2, e1501524 (2016).

[4] H. Ishizuka and N. Nagaosa, New J. Phys. 19, 033015 (2017).

[5] M. Nakamura, et al., Nature Commun. 8, 281 (2017).

[6] H. Ishizuka et al., Phys. Rev. Lett. 117, 216601 (2016).

[7] H. Ishizuka et al., Phys. Rev. B 95, 245211 (2017).

[8] Q. Ma et al., preprint (arXiv: 1705.00690).

 

Contact: Eun Gook Moon, Physics Dept., (egmoon@kaist.ac.kr)

20170831_Hiroaki Ishizuka.pdf

번호 일시 장소 연사 제목
260 4pm, 26th May  E6 1323  황민수 (Department of Physics, Korea University)  (광학분야 특별세미나)Topological photonic devices
259 4pm, 10th May  E6 1323  권혁준 (Korea Institute for Advanced Study, KIAS)  (광학분야 특별세미나)Testing quantum thermodynamics using quantum optics
258 4pm, 28th April  E6 1323  유경식 (KAIST 전기및전자공학부)  (광학분야 특별세미나)Adiabaticity and symmetry in optical waveguide design
257 4pm, 14th April  E6 1323  신승우 (KAIST 물리학과)  (광학분야 특별세미나)Holographic tomography of dielectric tensors at optical frequency
256 June 23th (Thur), 11:00  E6 Room(#1322)  Sun Yool Park(Joint Institute for Laboratory Astrophysics (JILA) & University of Colorado)  JILA’s search for the electron’s Electric Dipole Moment (eEDM) to probe physics beyond the standard model file
255 August. 16th (Fri), 14:00  E6 Room(#1323)  Jinxing Zhang  Multiferroic and Magnetoelectric Effects by Tailoring Interfacial Chemistry and Physics in Correlated Oxides file
254 August. 6th (TUE), 14:00  E6 Room(#1323)  Kanghyun Chu  Visualization of in-plane piezoresponse vector fields file
253 August. 1st (Thu), 14:00  E6 Room(#1323)  Hyeok Yoon  Low-density Superconductivity in SrTiO3 Probed by Planar Tunneling Spectroscopy file
252 May. 8th (Wed), 16:00  E6 Room(#1323)  Jieun Lee  Imaging valley dependent electron transport in 2D semiconductors file
251 Nov. 22th (Thur), 15:00  E6 Room(#1323)  Prof. Suprijadi Haryono  Experimental and Computational Study on Physical Properties based on Granular System file
250 May. 25th (Wed), 14:00  E6 Room(#2501)  Dr. Duk-Hyun Choe(Samsung Advanced Institute of Technology)  Atomic-level insights into ferroelectric switching and preferred orientation of ultrathin hafnia file
249 July 8(Mon), 14:00  E6, #1322  T. L. M. Guedes (Univ. of Konstanz)  Ultrabroadband squeezed pulses and their relation to relativity file
248 5. 30(월), 16:00  E6, #1501  공수현교수 (고려대학교 물리학과)  Light manipulation using 2D layered semiconductors
247 5. 23(월),16:00  E6, #1501  김준성교수 (postech 물리학과)  Novel electronic transport in topological van der Waals magnets
246 5.16(월),16:00  E6, #1501  조규붕교수 (HKUST)  Design synthetic topological matter with atoms and lights
245 5. 9(월),16:00  E6, #1501  김창영교수 (서울대)  Searching for new electronic properties in correlated material flatland
244 5. 2(월),16:00  E6, #1501  유상운교수 (한밭대)  What can we learn from the history of science and technology?(우리말강의)
243 4. 25(월), 16:00  E6, #1501  정영욱 책임연구원 (한국원자력연구원)  Ultrafast electron beam, a tool to explore the nanoscopic world of materials(우리말강의)
242 4. 11(월),16:00  E6, #1501  노재동교수 (서울시립대 물리학과)  Emergence of Statistical Mechanics in Quantum Systems
241 3. 28(월), 16:00  E6, #1501  이준희교수 (UNIST 에너지 및 화학공학부)  Ultimate-density atomic semiconductor via flat bands