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
228 2021-03-25 16:00  Online Seminar (Zoom)  Search for dark matter axion with Rydberg atoms file
227 2021-04-02 14:30  Online(Zoom)  Quantum computing and entanglement generation using trapped ions and photons
226 2021-04-02 16:00  Online(Zoom)  Van der Waals heterostructures for orbital gating-based phototransistors and electronic spectroscopy
225 2021-04-09 10:00  Zoom webinar  Integrated Lithium Niobate Photonics file
224 2021-04-19 19:00  Zoom webinar  Evidence of Electrical Switching in Antiferromagnets and Coherent Spin Pumping file
223 2021-05-14 14:30  Online seminar  Electrically tunable spin valve effect in vertical van-der-Waals magnetic tunnel junctions file
222 2021-05-14 16:00  Online seminar  Spatial and temporal separation of environmental dephasing sources from solid-state quantum emitters file
221 2021-05-17 17:00  Zoom webinar  Spin current generation and detection in uniaxial antiferromagnets file
220 2021-05-27 16:00  온라인  찾아가는 물리연구 현장(유럽 입자물리학연구소 소개) file
219 2021-06-08 10:00  Zoom webinar  Photonic crystal devices for sensing file
218 2021-06-11 14:30  Online seminar  Engineering sound waves and vibrations in multi-mode nanomechanical systems file
217 2021-06-11 16:00  Online seminar  Pseudogap in surface-doped black phosphorus file
216 2021-06-22 17:00  Zoom webinar  Spintronics meets Quantum Materials file
215 2021-07-29 14:00  Online seminar  Gravitationally Induced Dark Sector and Inflationary Dynamics file
214 2021-11-02 16:00  자연과학동(E6-2) #1323  Metrology of Band Topology via Resonant Inelastic X-ray Scattering file
213 2021-12-03 14:30  Zoom webinar  Topological Spin Textures: Skyrmions and Beyond file
212 2021-12-03 16:00  Zoom webinar  Nonequilibrium Heat Transport in Elemental Metals Probed by an Ultrathin Magnetic Thermometer file
211 2022-01-11 15:00  E6 #1501  Ultrafast optical studies on CDW collective modes of the Weyl-CDW (TaSe4)2I file
210 2022-01-12 11:00  Zoom and E6 #1323  Spectroscopic study of trapped ions towards probing dark matter and new physics file
209 2022-01-17 14:00  E6-2 Room 2502  Five Lectures on Observational Probes of Dark Energy file