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[Cancelled] Colloquium: Non-Equilibrium Strongly Hyperuniform Fluids with Large Local Density Fluctuations – Towards Perfect Photonic Fluids

Announcement: In view of the current situation in Hong Kong, please be informed that the Colloquium will be cancelled.


Disordered hyperuniform structures are an exotic state of matter having vanishing long wave-length density fluctuations similar to perfect crystals but without long-range order. Although its importance in materials science has been brought to the fore in the past decade, the rational design of experimentally realizable disordered strong hyperuniform micro-structures remains challenging. Here, by using computer simulations and theoretical analyses, we discover a new type of dynamic disordered fluid state with strong hyperuniformity in 2D systems of chiral active particles where particles perform independent circular motions of the radius R with the same handedness. In the strong driving or zero-noise limit, this system undergoes an absorbing-active transition to form a non-equilibrium strongly hyperuniform fluid. This new hyperuniform fluid features a special length scale, i.e., the diameter of the circular trajectory of particles, below which large density fluctuations as a result of dynamic cluster formation are observed. By developing a dynamic mean-field theory, we show that the dynamic cluster formation can be explained as an motility-induced microphase separation at mean-field level, while the Fickian diffusion at large length scales and local center of mass conserved interaction are responsible for the global hyperuniformity. Our results suggest the possibility of designing active matter system to form hierarchical disordered hyperuniform materials.


Dr. Ni received his PhD of Physics in 2012 from Utrecht University (the Netherlands) working with Prof. Marjolein Dijkstra focusing on the computational study on the self-assembly of colloidal systems. From 2012 to 2014, he did his postdoc with Profs. Martien A. Cohen Stuart and Peter G. Bolhuis focusing on the self-assembly of fibril-forming polypeptides. In 2014, he was awarded the NOW VENI fellowship which is the most prestigious personal grant for young scientists in the Netherlands to start independent research lines. In March 2016, he joined the School of Chemical and Biomedical Engineering in Nanyang Technological University as an assistant professor. In 2016, he was awarded the Best Research Prize by the European Cooperation in Science and Technology (COST) Action – Flowing Matter (An annual prize for European Early Stage Researchers in soft matter within eight years after the date of PhD). His research has been published in a number of top scientific journals, e.g. Nature Communications, Science Advances. PNAS, PRL, ACS Nano, Soft Matter, etc.

Event Details
Dr Ran Ni
Assistant Professor, School of Chemical and Biomedical Engineering, Nanyang Technological University

Date & Time
29 November 2019 3:00 pm

G4302 Yeung Kin Man Academic Building, City University of Hong Kong

Dr DAI Liang (34426025