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
404 2017-04-28 14:30  E6-2. 1st fl. #1323  Hot electron generation at surfaces and its impact to catalysis and renewable energy conversion
403 2017-04-28 16:00  #1323 (E6-2. 1st fl.)  Carbon nanotubes coupled to superconducting impedance matching circuits
402 2016-04-28 15:00  #2501(E6-2. 2nd fl.)  Lattice/Spin/Charge Coupling in 5d Pyrochlore Cd2Os2O7
401 2016-04-05 16:00  E6-2. 1st fl. #1322  A new impurity solver for multi-orbital systems: adaptive truncation of the Hilbert space
400 2023-04-06 16:00  E6-2 #1323  (광학분야 세미나)Nanophotonics-based approaches to explore Berry physics
399 2021-04-09 10:00  Zoom webinar  Integrated Lithium Niobate Photonics file
398 2019-04-19 11:00  #1323, E6-2  First-principles studies of semiconductors for solar cell applications file
397 2023-04-28 11:00  E6 #1323  Tkachenko wave: From the modern field theory viewpoint
396 2022-04-08 11:00  E6-1 #1323  (응집물리 세미나) Flat-surface-assisted physical phenomena occurring in single crystal metal thin film file
395 2019-04-11 16:00  #1323, E6-2  Massive screening for cathode active materials using deep neural network file
394 2018-04-11 13:30  #1323 (E6-2, 1st fl.)  Probing 3D Structure and Physical Properties of Materials at the Single-Atom Level file
393 2018-04-11 16:00  #1323 (E6-2, 1st fl.)  Non-Gaussian states of multimode light generated via hybrid quantum information processing file
392 2018-04-13 10:00  #1323 (E6-2, 1st fl.)  Quantum meets Mechanics: from Quantum Information to Fundamental Research file
391 2023-04-13 11:00  Zoom  [High Energy Theory Seminar]Noninvertible Gauss Law and Axions
390 2022-04-15 11:00  Online seminar  (응집물리 세미나) First-principles studies of polar oxides and their applications file
389 2019-04-23 16:00  #1323, E6-2  From Mott physics to high-temperature superconductivity file
388 2019-04-26 16:00  #1323, E6-2  Robust Quantum Metrology using Strongly Interacting Spin Ensembles and Quantum Convolutional Neural Network file
387 2016-04-26 16:00  #1323(1st Floor. E6-2)  Transport spectroscopy for electronic bands in carbon-based nanomaterials with weak-bond contacts
386 2023-04-27 11:00  E6-2 #1322  Inverse Shapiro steps and coherent quantum phase slip in superconducting nanowires
385 2019-04-04 16:00  #1323, E6-2  Chiral spin-photon interaction at nanoscale file