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
406 2021-11-02 16:00  자연과학동(E6-2) #1323  Metrology of Band Topology via Resonant Inelastic X-ray Scattering file
405 2023-11-01 16:00  E6-2, #2502  [High Energy Theory Seminar] Modular functions and 3D N=4 rank-zero superconformal field theories
404 2016-11-1 10:30  #1323(E6-2 1st fl.)  Time scale dependent dynamics in InAs/InP quantum dot gain media
403 2016-11-18 10:30  #5318(5th fl.)  Non-equilibrium many-body spin dynamics in diamond
402 2022-11-18 16:00  E6-2. 1st fl. #1323 & Zoom  Qubits, new experimental tools for physics file
401 2022-11-18 14:30  E6-2. 1st fl. #1323 & Zoom  Kondo cloud condensation in a highly-doped semiconductor metal file
400 2022-11-17 16:00  E6-2 #1323  (광학분야 세미나) Ultrastructural and Spectroscopic Studies by Super-Resolution Fluorescence Microscopy
399 2023-11-16 16:00  E6-2(Natural Science B/D). 1st fl. #1323  Electric-field control of emergent phenomena in correlated oxide thin films
398 2016-11-16 16:00  #1323(E6-2. 1st fl.)  Realizing Haldane Model in Fe-based Honeycomb Ferromagnetic Insulators
397 2020-11-12 16:00  E6-2 1323  2020 가을학기 광학분야 특별세미나
396 2016-11-11 13:30  #1323(E6-2. 1st fl.)  Bandgap Engineering of Black Phosphorus
395 2016-11-11 16:00  #1323(E6-2. 1st fl.)  Dirac fermions in condensed matters
394 2022-11-11 11:00  E6-2 #1323  [Update 세미나영상] (응집물리 세미나) Honeycomb oxide heterostructures for quantum spin liquid file
393 2016-11-10 16:00  E6-2. #1323(1st fl.)  Low Dimensional Active Plasmonics and Electron Optics in Graphene
392 2022-11-10 16:00  E6-2. 1st fl. #1323  Probing the Origin of Cosmic Infrared Background and Future Prospects with SPHEREx
391 2016-11-01 14:30  Seminar Room #1323(E6-2)  Search for dark sector particles in the B-factory experiments
390 2019-11-01 16:00  E6-2. 1st fl. #1323  Electron transport through weak-bonded contact metal with low dimensional nano-material file
389 2019-11-01 14:30  E6-2. 1st fl. #1323  Squeezing the best out of 2D materials file
388 2016-11-04 15:00  E6-2. #1323(1st fl.)  Quantum information experiments using few electron spins in semiconductors
387 2016-11-04 13:30  E6-2. #1323(1st fl.)  Exotic phenomena at oxide LaAlO3/SrTiO3 hetero-interface and their applications