香港科技大学物理系韩一龙博士访问我组 2008-1-16

报告人：

韩一龙 博士。1998年北京大学物理系本科毕业后，在芝加哥大学攻读博士学位。之后在美国宾西法尼亚大学做博士后。2007年夏天，被香港科技大学物理系聘为助理教授。研究方向是实验软物质物理，主要用胶体颗粒作为原子模型系统研究统计物理中的一些问题，包括胶体晶体融化和结晶、椭球的布朗运动、位形温度、胶体自组装和图案形成、伊辛自旋阻错等。

报告题目：Geometrical frustration in colloidal “antiferromanget”

摘要:
We report experiments about a self-organized colloidal system that exhibits geometrical frustration similar to that of antiferromagnetic Ising spins on a triangular lattice. Novel thermally sensitive microgel NIPA (N-isopropyl acrylamide) spheres are close packed between two parallel flat walls with a vertical separation of about 1.5-particle diameters. The particles form an approximate in-plane triangular lattice. Neighboring particles tend to push each other toward opposite walls leading to out-of-plane local up and down buckling. We tune the strength of such effective antiferromagnetic interactions by varying temperature-tunable diameter of spheres. “Spin” flipping was directly visualized with video microscopy. We investigated the static structures, the dynamics of particles with different degrees of frustration and the degenerated ground state. This experiment is the first dynamic measurement in a geometrical frustrated system at single-particle resolution.