2022 Fiscal Year Research-status Report
Ultrafast femtosecond laser control of electron dynamics in two-dimensional strong spin-orbit coupling materials
| Project/Area Number |
22K13991
|
|---|
| Research Institution | National Institutes for Quantum Science and Technology |
|---|
Principal Investigator |
Hashmi Arqum 国立研究開発法人量子科学技術研究開発機構, 関西光科学研究所 光量子科学研究部, 博士研究員 (90815325)
|
|---|
| Project Period (FY) |
2022-04-01 – 2024-03-31
|
| Keywords | Spin-orbit interactions / TDDFT / Nonlinear optics / Ultrafast |
|---|
| Outline of Annual Research Achievements |
By using Time-dependent density functional theory (TDDFT) based on the Maxwell-TDDFT scheme, the combined classical Maxwell plus time-dependent Kohn-Sham (TDKS) equations are used to describe the propagation of electromagnetic fields. Regarding the ultrafast electron dynamics in 2D layers of Transition metal dichalcogenides, I investigated the carrier dynamics in terms of valley polarization in WSe2 monolayer via single and two-color laser field.
The valley selection rules suggest that linearly polarized light couples equally to both valleys and valley polarization cannot be achieved by a linearly polarized field. My study is focused on the above-mentioned argument and we aimed to induce valley asymmetry by linearly polarized pulses which are considered not achievable by a linearly polarized field.
It is possible to create an asymmetric laser field by mixing a fundamental frequency and its second harmonic. The two pulses intensity ratio and the relative carrier-envelope phase (CEP) control the valley polarization. I compared the valley polarization results of two-color laser scheme results with the single color pulse. I found that the valley polarization via two-color control exceeds the single-color scheme by 1.2 times as the two-colors field exhibits more asymmetry in its temporal shape. The results reveal a convenient new path toward the optical control of valley pseudospins.
|
| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
I have established a theoretical view point by using the formalism of TDDFT with Maxwell equations to show the sub-cycle control of electron dynamics in very thin layers in transition metal dichalcogenides monolayers.
The above mentioned work shows the possibility of controlling the carrier dynamics of up to femtosecond time scale through the ultrashort pulses so the first part of our project is completed. The research on the topological insulator which is the second part of the project is in progress.
|
| Strategy for Future Research Activity |
Regarding the work on toplogical insulator, I will investigate the Bi2Se3 bulk and thin layer system consisting of 3 layers. Using TDDFT calculations, various linear and nonlinear optics functionalities on the bulk and layer system will be explored.
The intial work shows potential regarding project focus on ultrafast control of carrier dynamics in toplogical insulator.
|
