时间：2016年9月29日（星期四）上午9：00
地点：材料科学与工程学院8号楼2楼会议室

报告摘要：
       Over recent years, laser-induced ultrafast structural dynamics in nanocrystals have been a subject of considerable study using time-resolved optical pump-probe techniques. The remarkable dynamics phenomena due to transient responses of electrons and phonons in nanostructures have been attractive to researchers. Recently, the structural stability, elastic, and thermal properties were studied via the observation of vibration features of their confined phonon modes. Particular phonon modes with (totally symmetric) radial in-phase vibration and low frequencies, the so-called photoinduced modes, can be excited abruptly by ultrafast laser heating due to much shorter heating time as compared with their oscillation period. The photoinduced modes in nanocrystals can be calculated using a continuum method based on an isotropic elastic model. Even though the calculated frequencies from the continuum model have a good agreement with experimental results, their displacement patterns of atoms are incorrect after considering the crystal structure of metal nanocrystals. In this report, we adopt a theoretical method based on a realistic atomistic model and group theory to study the crystallinity-dependent vibrational properties of photoinduced modes in silver nanoprisms. Group theory is applied not only can reduce dramatically the computational effort required for matrix diagonalization but also can classify the phonon modes in nanocrystals according to their symmetry properties.

附报告人简介：
       吴民耀教授,马来西亚华人，台湾师笵大学(NTNU)物理学系取得学士和博士学位。专长为纳米结构固态理论，近场光学理论和计算物理学。研究方向是利用电脑模拟的方法研究金属纳米结构的局域化表面电浆子结构的近场光学特性(near-field optical properties)及其应用于高密度光学储存系统和光纤型生物感测技术(fiber-based biosensor system)。2009年开始，在台湾中央研究院应用科学研究中心(Research Center for Applied Sciences, Academia Sinica)担任院内博士后研究员，研究的项目有：(1) 金属纳米结构的近场光学特性和局域化声子(localized phonons)振动模式特性研究。(2)第二型半导体量子点(GaAs/GaSb quantum dots)和量子环(GaAs/GaSb quantum rings)的光学和电子结构特性以及其应用于纳米激光相关技术研究。由于研究工作上的需要，已累积多年的编写科学计算程序的经验.自主发展多套针对纳米材料的光学和半导体特性研究且高度并行化的高效能科学仿真软件，目前在广州高能计算机科技有限公司，担任HPC技术总经理。