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Phase-Space Networks and Colloidal Experiments of Frustrated Spin Models

Speaker:Dr. Yilong Han
Affiliation:Department of Physics, Hong Kong University of Science and Technology
Date:March 28, 2011
Time:5:00 - 6:30 p.m.
Venue:Lecture Theatre T2, Meng Wah Complex, HKU


We fabricated a self-assembled colloidal monolayer that exhibits geometrical frustration similar to that of antiferromagneticIsingspins on a triangular lattice. Video microscopy reveals the single-“spin” dynamics in the geometrically frustrated system for the first time. We also theoretically introduced a network approach to study the phase spaces of the following models with discrete degrees of freedom: the antiferromagneton triangular lattice, the six-vertex model (i.e. square ice), 1D and 2D lattice gases. The phase spaces were fully mapped as discrete networks such that quantitative network analysis can be applied to phase-space studies. The resulting phase spaces, in turn, establish a new class of complex networks with unique topology characterized by the Gaussian spectral density and novel fractal structures. The phase spaces of different models with different boundary conditions share some common features. The network’s community analysis could provides a quantitative measure of weak ergodicityand the fractal structures of phase spaces cast light on Tsallisentropy. One by-product in the phase-space construction is a one-to-one mapping between two dimensional jigsaw puzzles (i.e. the six-vertex model) and three dimensional sphere stacks. 

About the Speaker:

Dr. Han's research interests include experimental soft matter physics and statistical physics. He got the BS degree from Peking University and Ph.D. degree from the University of Chicago. Now he is an assistant professor at Hong Kong University of Science and Technology.


Physics colloquium series is organized to introduce cutting edge researches and new development in physics, designed to be suitable to graduate and undergraduate students, and also to scientists working on different fields. Each colloquium will generally start with an extensive introduction of the background of the field, followed by forefront research topics and results. The colloquium will serve as an education forum for students and laymen alike, and also serve as a platform for exchange and update their knowledge of various branches of physics among academic staff members.

Poster of the Colloquium