visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나
날짜 2017-08-31 14:00 
연사  
장소 #5318(E6-2. 5th fl.) 

“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 연사 제목
공지 2025-02-24 16:00    2025년 봄학기 콜로키움 안내
공지 2025-02-27 16:00    2025년 봄 물리학과 특별세미나 (광학/응집물리 분야)
614 2009-02-23 16:00    Physics Colloquium : 2009 Spring file
613 2009-09-07 16:00    Physics Colloquium : 2009 Fall file
612 2009-10-21 16:00    Interdimensional Universality of Dynamic Interfaces
611 2010-02-08 16:00    Physics Ciolloquium : 2010 Spring file
610 2010-02-14 16:00    Physics Colloquium - 2011 Spring file
609 2010-09-06 16:00    Physics Colloquium : 2010 Fall file
608 2011-05-16 16:00    Photonics with surface plasmon polaritons
607 2011-09-03 16:00    Physics Colloquium : 2011 Fall file
606 2012-02-13 16:00    Physics Colloquium : 2012 Spring
605 2012-04-02 16:00    A new route to ferroelectricity in magnetic spinels: a case of Co2MnO4
604 2013-03-11 16:00    Physics Colloquium : 2013 Spring
603 2013-09-09 16:00    Physics Colloquium : 2013 Fall
602 2014-03-10 16:00    Physics Colloquium : 2014 Spring file
601 2014-05-28 17:00    부품소재산업이 미래다
600 2014-12-22 14:00    Dynamics of molecular motors: Power stroke vs Brownian ratchet file
599 2015-03-04 12:00    Bioimaging and Biosensing Using Near-Infrared Fluorescence file
598 2015-03-09 16:00    Physics Colloquium : 2015 Spring file
597 2015-03-13 14:00    The 15th Innovative Workshop on Soft/Bio Materials file
596 2015-06-03 12:00    The First Wednesday Multidisciplinary Forum file
595 2015-07-15 14:00    Electronic and optical properties of titanate-based oxide superlattices