visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나
날짜 2017-08-31 14:00 
일시 AUG. 31 (Thu.), 2 PM 
장소 #5318(E6-2. 5th fl.) 
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 날짜 장소 제목
527 2010-02-14 16:00  E6, 1501  Physics Colloquium - 2011 Spring file
526 2023-04-14 12:00  E6-2 #1323  (응집물리 세미나)Exotic quantum phenomena in two-dimensional materials file
525 2023-05-12 11:00  E6-2 #1323  (응집물리 세미나)Interlayer conductivity and plasmon in weakly coupled layered systems
524 2022-05-26 16:00  E6 1323  (광학분야 특별세미나)Topological photonic devices
523 2023-06-01 16:00  E6-2 #1323  (광학분야 세미나)Quantum sensing using a squeezed light from hot Rb vapor
522 2015-03-09 16:00  E6, 1501  Physics Colloquium : 2015 Spring file
521 2022-03-31 16:00  online  (광학분야 특별세미나)Ultrafast time-resolved spectroscopy in topological materials
520 2023-03-30 16:00  E6-2 #1323  (광학분야 세미나)Scalable quantum entanglement in trapped-ions based quantum computer
519 2022-08-17 11:00  E6-6 #118호  Robust Hamiltonian Engineering of Large Quantum Systems (큰 양자시스템의 견고한 해밀토니안 엔지니어링)
518 2010-02-08 16:00  E6, 1501  Physics Ciolloquium : 2010 Spring file
517 2009-10-21 16:00  E6, 1501  Interdimensional Universality of Dynamic Interfaces
516 2010-09-06 16:00  E6, 1501  Physics Colloquium : 2010 Fall file
515 2017-03-21 16:00  Seminar Room 1323  Spring 2017: Physics Seminar Serises file
514 2022-05-16 16:00  E6, #1501  Design synthetic topological matter with atoms and lights
513 2020-10-15 16:00  (https://kaist.zoom.us/j/93997220310)  Towards resource-efficient and fault-tolerant quantum computation with nonclassical light
512 2022-04-25 16:00  E6, #1501  Ultrafast electron beam, a tool to explore the nanoscopic world of materials(우리말강의)
511 2017-12-13 13:30  자연과학동 대형강의실 (1501호)  KAIST-KIAS Joint Workshop in Theoretical Sciences 개최 file
510 2019-05-21 16:00  #5318, E6-2  Classification of flat bands according to the band-crossing singularity of Bloch wave functions file
509 2019-09-02 16:00  Seminar Room 1501  Fall 2019: Physics Colloquium file
508 2023-05-26 11:00  E6-2 #1323  (응집물리 세미나)Spectral Analyses of Stochastic Charge Trapping in Oxide Heterostructures file