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
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
19 2015/03/09-06/08  E6, 1501  최현용교수(연세대) 외12명  Physics Colloquium : 2015 Spring file
18 2015/03/13, 2PM  Connect Room, KI Bldg.    The 15th Innovative Workshop on Soft/Bio Materials file
17 2015/03/04, 12PM  1323호, E6-2  Prof. Choi Hak-Soo(Harvard)  Bioimaging and Biosensing Using Near-Infrared Fluorescence file
16 2014/12/22, 2PM  E6, Rm1319  Prof. Changbong Hyeon (KIAS)  Dynamics of molecular motors: Power stroke vs Brownian ratchet file
15 2015/09/15-12/08  E6, 1501  박제근 교수(서울대 물리학과) 외12명  Physics Colloquium : 2014 Fall file
14 2014/05/28, PM5  KI Building, Matrix Hall  이웅범 대표이사(LG이노텍)  부품소재산업이 미래다
13 2014/03/10-06/09  E6, 1501  신용일교수(서울대)  Physics Colloquium : 2014 Spring file
12 2013/09/09-12/09  E6, 1501  박혁규교수(부산대) 외  Physics Colloquium : 2013 Fall
11 2013/03/11-06/10  E6, 1501  강명수교수(KAIST) 외  Physics Colloquium : 2013 Spring
10 2012/04/02, 4PM  E6, 1501  Yong Hee Jeong  A new route to ferroelectricity in magnetic spinels: a case of Co2MnO4
9 2012/02/13-05/14  E6, 1501  Kenji Ohmori (Photo-Molecular Science, IMS)  Physics Colloquium : 2012 Spring
8 2011/09/03-12/06  E6, 1501  김용균교수(한양대) 외  Physics Colloquium : 2011 Fall file
7 2011/05/16, 4PM  E6, 1501  서민교교수(KAIST)  Photonics with surface plasmon polaritons
6 2010/02/14-05/09  E6, 1501  황철주(주성엔지니어링 사장) 외  Physics Colloquium - 2011 Spring file
5 2010/09/06-12/06  E6, 1501  조호진기자(조선일보) 외  Physics Colloquium : 2010 Fall file
4 2010/02/08-05/03  E6, 1501  최인수교수(서울대) 외  Physics Ciolloquium : 2010 Spring file
3 2009/10/21, 4PM  E6, 1501  최석봉교수(서울대)  Interdimensional Universality of Dynamic Interfaces
2 2009/09/07-11/30  E6, 1501  이주영박사(KIAS) 외  Physics Colloquium : 2009 Fall file
1 2009/02/23-05/04  E6, 1501  안종현교수(성균관대) 외  Physics Colloquium : 2009 Spring file