Major research fields
Quantum Materials Science, Quantum Materials Design
Crystals including transition-metal (TM) ions or rare-earth (RE) ions are utilized as luminescent materials for laser crystals, electronic displays, lighting devices, and so on. However, in the development of next generation devices such as 3-dimensional displays and white LED lighting systems, development of novel luminescent materials with improved properties are constantly desired. Some of the luminescent materials are also known as precious gem stones. For example, ruby is a well-known beautiful gem stone but it is also technologically important as a laser crystal. In our laboratory we have developed a computer software to predict the optical spectra of these materials theoretically. Since TM ions and RE ions work as emission centers in luminescent materials, we calculate the local electronic structure around these ions and investigate the factors which determine their optical properties. Since such calculations are very demanding, we use high-performance computers for systematic calculations. We also conduct research on the theoretical design of novel luminescent materials or gem stones based on systematic calculations of fictitious materials. If we can theoretically find a highly promising material, we also try to synthesize the actual crystal using the crystal growth equipment and investigate its physical properties experimentally.
Major relevant publications
- First-principles and experimental analysis of fn-fn-1d1 absorption spectra and multiplet energy levels of Pr3+, Nd3+, and U3+ in LiYF4, S. Watanabe, K. Ogasawara, M. Yoshino, and T. Nagasaki, Phys. Rev. B 79 (2010) 125128, 18 pages.
- First-principles calculation of ground and excited-state absorption spectra of ruby and alexandrite considering lattice relaxation, S. Watanabe, T. Sasaki, R. Taniguchi, T. Ishii, and K. Ogasawara, Phys. Rev. B 79 (2009) 075109, 9 pages.
- First-principles calculations of 4fn-4fn-15d transition spectra, K. Ogasawara, S. Watanabe, H. Toyoshima, M.G. Brik, "Handbook on Physics and Chemistry of Rare Earths" Vol. 37, Chapter 231 (Elsevier,2007).