2016 Fiscal Year Research-status Report
Ultrafast dynamics and resonance effects in photoemission from surfaces
| Project/Area Number |
16K05393
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| Research Institution | Chiba University |
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Principal Investigator |
KRUEGER PETER 千葉大学, 大学院融合科学研究科, 教授 (30706362)
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| Project Period (FY) |
2016-04-01 – 2020-03-31
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| Keywords | 光物性 / 表面・界面 |
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| Outline of Annual Research Achievements |
(1)In order to understand ultrafast electron dynamics in solids, time delay in photoemission from surfaces is investigated theoretically. In the first year we have simulated the scattering of an electron wave packet at a potential barrier by solving the time-dependent Schroedinger equation and have extracted the time delays numerically. Good agreement with the known analytical results have been obtained. We are now extending the model to multiple barriers to and compare with the time-independent multiple scattering theory. Moreover, time delay in photoemission from a Cu surface was estimated from the group velocities obtained from DFT band structure calculations and the results were compared with the experiments of our research partner at the ETH Zurich. A joint publication has been submitted.
(2) Non-resonant angle-resolved photoemission spectra of a BiAg2 Rashba system were obtained from the DFT band structure by explicitly calculating the high energy final states and the transition matrix elements. For the boundary conditions of the final state wave function, several approximations have been compared, but were found not satisfactory for the photoemission problem. This will now be improved by matching the waves obtained from the DFT supercell method with the exact solutions in the asymptotic vacuum region.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
The main objectives of the first year has been met.
Good progress was made for the photoelectron time delay problem both in the simulation of the wave packet dynamics and the band structure approach.
In particular, time delays for a Cu surface were obtained in a 3-step model by calculating the group velocities from the DFT band structure. This part of the project was planned for year 3, but has already been achieved.
A joint publication with the experimental group in Switzerland has been submitted and is being reviewed.
As for second aspect of the project (resonance effects in photoemission) we have run a little late. This is because it was found out by our experimentalist colleagues (Group of F. Reinert, Germany) that the strong photon-energy dependence observed in BiAg2 is NOT a resonance effect, contrary to what they had claimed before. Therefore we shall change the focus of our project to non-resonant ARPES and to resonant Auger emission spectroscopy, for which many new experimental results exist.
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| Strategy for Future Research Activity |
During the next year, the following plan will be carried out.
1) Photoemission time delay: a) Comparison between time delays obtained from the wave packet simulations with those from the phase shifts (Wigner delay) for a long chain of periodic barriers. b) Ab initio calculation of Wigner delays for noble metal surfaces in a 1-step model by extending our multiple scattering theory to extract the phases of the final state wave functions.
2) Resonant effects in photoemission: Calculation of the atomic (primary) wave in resonant Auger electron emission from a atomic multiplet approach for transition metal atoms. A general program will be developed for any transition metal atom. The results will be tested for Cu (3d10 4s1) and Ni(3d9 4s1) where some analytical solutions exist in the literature.
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| Causes of Carryover |
In the first year we have purchased a computer workstation for about 1000000 Yen, as planned. However, half of the cost was covered from another research budget, where we could obtain 500000 Yen for hardware. As this amount is not sufficient for buying a workstation, we decided to share the cost of the workstation between the two budgets.
Thereby we could save about 400000 Yen for the following years of this project.
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| Expenditure Plan for Carryover Budget |
The saved budget of 400000 Yen will be used for upgrading important simulation software packages buying a new program (Wien2k) and for repairing the oldest workstation in our laboratory.
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Research Products
(3 results)
