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
160 Dec. 8(Thu) 4p.m.  #1323(E6-2. 1st fl.)  Dr. Jinhyoung Lee, Hanyang University  Dynamical Resonance between Two Optical Cavities via Optomechanical Oscillator
159 Dec. 7 (Fri.), 04:00 PM  E6-2. 1st fl. #1323  Dr. Joon Ho Jang  Novel probes of interacting electrons in 2D systems file
158 Dec. 7 (Fri.), 02:30 PM  E6-2. 1st fl. #1323  Dr. Gyung Min Choi  Spin generation from heat and light in metals file
157 Dec. 3 (Fri.), 04:00 PM  Zoom webinar  Dr. Hyejin Jang (Seoul National University)  Nonequilibrium Heat Transport in Elemental Metals Probed by an Ultrathin Magnetic Thermometer file
156 Dec. 3 (Fri.), 02:30 PM  Zoom webinar  Dr. Soong-Geun Je(Chonnam National University)  Topological Spin Textures: Skyrmions and Beyond file
155 DEC. 27 (Thu), 04:00 PM  E6-2. 1st fl. #1323  Prof. Na Young Kim  Quantum Innovation (QuIN) Laboratory file
154 Dec. 26 (Wed.), 04:00 PM  E6-2. 1st fl. #1323  Dr. Isaac H. Kim  Brane-like defect in 3D toric code file
153 DEC. 26 (Wed), 04:00 PM  E6-1. 3rd fl. #3434  Y. Kim, A. Go, K. Hwang and E.-G. Moon  Informal Workshop on Topology and Correlation file
152 DEC. 16~18 (Sun~Tue)  E6-2. 1st fl. #1323  Prof. Keisuke Totsuka  Lectures on 2d Conformal Field Theory file
151 Dec. 15 (Fri.), 9:20 AM  E6-2, Lecture Room #1323  Prof. Jhinhwan Lee 외 9명  Workshop on Magnetism in Unconventional Superconductors 개최 file
150 Dec. 13-14(Wed.-Thu.) 13:30 PM  자연과학동 대형강의실 (1501호)  장기주 교수 외 9명  KAIST-KIAS Joint Workshop in Theoretical Sciences 개최 file
149 Dec. 12th (Mon)  1:30p.m. #1323(E6-2. 1st fl.)  Dongjoon Song , AIST  “Possible symmetry in the phase diagrams of electron- & hole-doped cuprate high-Tc superconductors”
148 DEC. 11 (Tue), 04:00 PM  E6-2. 1st fl. #1323  Prof. Hiroshi Shinaoka  Natural compact representation of Matsubara Green’s functions: applications to analytic continuation and quantum many-body simulations file
147 Dec. 11 (Fri.), 04:00 PM  online  Hyobin Yoo(Sogang Univ.)  Atomic and electronic reconstruction at van der Waals interface in twisted 2D materials
146 Dec. 11 (Fri.), 02:30 PM  online  Myung Hwa Jung(Sogang Univ.)  Antisymmetric interlayer exchange coupling in magnetic multilayers
145 Dec 27 (Fri), 3:00 PM  #5318, E6-2  Han Gyeol Suh  The superconducting order parameter puzzle of Sr2RuO4 file
144 August. 6th (TUE), 14:00  E6 Room(#1323)  Kanghyun Chu  Visualization of in-plane piezoresponse vector fields file
143 August. 1st (Thu), 14:00  E6 Room(#1323)  Hyeok Yoon  Low-density Superconductivity in SrTiO3 Probed by Planar Tunneling Spectroscopy file
142 August. 16th (Fri), 14:00  E6 Room(#1323)  Jinxing Zhang  Multiferroic and Magnetoelectric Effects by Tailoring Interfacial Chemistry and Physics in Correlated Oxides file
141 August. 14th (Wed.), 4:00PM,  Rm. 1323, E6  Prof. Nicolas Treps  Quantum Optics, at the heart of quantum metrology and quantum information file