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
206 2018-02-12 15:00  #C303, (Creation Hall 3F, KAIST Munji Campus)  The recent result of XMASS Experiment
205 2017-02-01 14:00  #1323(E6-2. 1st fl.)  Quantum electron optics using flying electrons
204 2019-12-05 16:00  #1323, E6-2  Subwavelenth Photonic Devices: From Single Photon Sources to Solar Cell file
203 2019-12-03 16:00  #1323, E6-2  Toward Quantum Materials with Correlated Oxides file
202 2019-12-27 15:00  E6-2,#5318  The superconducting order parameter puzzle of Sr2RuO4 file
201 2020-12-02 10:00  Zoom  Recent progress in Axion Dark Matter eXperiment (ADMX) technology file
200 2019-12-18 16:00  #1323, E6-2  Road to Higher Tc Superconductivity file
199 2019-12-13 13:30  #1323, E6-2  Biophysics Mini-symposium at KAIST file
198 2019-12-13 13:00  #2501, E6-2  Computational Material Designs: Current Status and Future Directions file
197 2023-12-14 16:00  CAPP Seminar Room C303, Creation Hall, KAIST Munji Campus  Superconducting qubits for large-scale quantum computers file
196 2020-12-09 10:00  Zoom  Searching for the QCD axion with the ARIADNE experiment file
195 2020-12-23 10:00  Online  Online workshop for Quantitative Phase Imaging file
194 2020-12-10 13:55  Zoom  Consistency of Boltzmann equation and light dark matter from inflaton decay
193 2016-12-09 16:00  #1323(E6-2. 1st fl.  Shift Charge and Spin Photocurrents in Dirac Surface States of Topological Insulator
192 2016-12-09 13:30  #1323(E6-2. 1st fl.)  Entanglement area law in strongly-correlated systems
191 2022-12-09 11:00  E6-2 #1323  [Update 세미나영상](응집물리 세미나) Single-shot measurements of strongly-correlated artificial molecular levels in semiconductor quantum dots file
190 2016-12-8 16:00  #1323(E6-2. 1st fl.)  Dynamical Resonance between Two Optical Cavities via Optomechanical Oscillator
189 2022-12-07 16:00  E6-2 #1323  (광학분야 세미나) Non-Hermitian physics and non-Hermitian singularity
188 2018-12-07 16:00  E6-2. 1st fl. #1323  Novel probes of interacting electrons in 2D systems file
187 2018-12-07 14:30  E6-2. 1st fl. #1323  Spin generation from heat and light in metals file