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 Sep.22 2022  E6-1 #1323    2022 가을학기 응집물리 및 광학 세미나 전체 일정
143 Oct. 4th(Tuesday) at 4:00 PM  E6 #2501  Prof. Craig Lawrie (Deutsches Elektronen-Synchrotron DESY)  Distinguishing 6d (1, 0) SCFTs new
142 10AM, 29th Mar. / 13:30 PM, 30th Mar.  E6 #1501/zoom, E6 #2502/zoom  Dr. RYO HANAI (APCTP)  Non-reciprocal phase transitions file
141 10AM, 31th Mar.  E6 #1501/zoom  Dr. Samuel Begg (APCTP)  Weiss fields for Quantum Spin Dynamics file
140 Jan. 25th (Tue), 15:00  E6 #1501/online  Junhyun Lee (Rutgers, the State University of New Jersey)  Emulating twisted double bilayer graphene with a multiorbital optical lattice file
139 Jul. 14th (THU), 14:15  E6 #1501 & Zoom  Dr. Hyeong Jun LEE(Institute of Natural Science, KAIST)  Hund and electronic correlations in ruthenium-based systems
138 Jul. 14th (THU), 13:30  E6 #1501 & Zoom  Dr. Jahyun Koo(Institute of Natural Science, KAIST)  Electronic structure and anomalous transport properties of topological materials by first principle calculation
137 Aug. 1st(Mon), 10:00AM  E6 #1501 & Zoom  손상모 박사(Space Telescope Science Institute (STScI)  [Update 세미나 영상] James Webb Space Telescope & OTE Commissioning
136 Jul. 14th (THU), 15:00  E6 #1501 & Zoom  Dr. Sunghun Kim(Institute of Natural Science, KAIST)  Pure two-dimensional quantum electron liquid and its phase transition
135 Jan. 11th(Tue), 15:00  E6 #1501  Soyeun Kim(UIUC)  Ultrafast optical studies on CDW collective modes of the Weyl-CDW (TaSe4)2I file
134 Jan. 26th (Tue), 13:00  E6 #1501  Dr. Hyojin Jung (NIMS)  An Introduction to Cohomology groups file
133 Apr. 13(Wed.) 10:30Am  E6 #1323/zoom  Mingu Kang (Max Planck POSTECH Korea Research Initiative)  Harnessing topology and correlations from singularities in 3d-kagome metals
132 Oct. 6th(Thursday) at 1:00 PM  E6 #1323  Dr. Monica Jinwoo Kang (Caltech)  Counting States with Global Symmetry new
131 2015/07/23,1:30PM  E4, B401  Prof. Gilles Lérondel (Univ. of Technology of Troyes)  Enhanced ZnO based UV photonics and related applications file
130 2015/12/17, 11:00AM  E4(KI Building), Matrix Hall (2nd fl.)  Dr. Jung-Hoon Park (Purdue University)  Wavefront engineering for in-vivo Deep brain imaging
129 2015/12/09, 11AM  E4(KI Building), Connect room (2nd fl.)  Arjun G. Yodh (University of Pennsylvania)  Functional Imaging & Monitoring of Brain & Breast with Diffuse Light
128 2015/03/13, 2PM  Connect Room, KI Bldg.    The 15th Innovative Workshop on Soft/Bio Materials file
127 Sep. 21, Wed. 4:00 PM  College of Natural Science E6-2, Rm. 1323  Prof. Duk-Yong Choi (Australian National University)  Materials and Device Nanofabrication of Optical Metasurfaces file
126 July 21, 2022 (Thu) 4:00 PM(KST)  CAPP Seminar Room C303, Creation Hall, KAIST Munji Campus  Prof. Jihn E. Kim (Kyoung Hee University)  Quintessential axions file
125 October 15, 2020 (Thursday  CAPP Seminar Room #C303, Creation Hall (3F), KAIST Munji Campus  Prof. Gil-Ho Lee (POSTECH)  Graphene-based Josephson junction microwave bolometer file
124 Jun. 1(Wed) 10:30 AM  BK21 Conference Room (#1318, E6-2)  Dr. Noriaki Horiuchi, Editor, Nature Photonics  Welcome to Nature Photonics