Professor Salvatore Torquato
Dept. of Chemistry, Dept. of Physics, Princeton Institute for the Science and Technology of Materials, and Applied & Computational Mathematics
Thursday, June 7, 15:30 - 16:30
Building 227, Room A202
Thursday, June 7, 13:30 - 14:30
Building 1 Room 4058
Host: Michael Mascagni
Abstract: While there are four commonly observed states of matter (solid crystal, liquid, gas, and plasma), we have known for some time now that there exist many other forms of matter. Disordered hyperuniform many-particle systems  can be regarded to be new states of disordered matter in that they behave more like crystals or quasicrystals in the manner in which they suppress large-scale density fluctuations, and yet are also like liquids and glasses because they are statistically isotropic structures with no Bragg peaks. Thus, disordered hyperuniform systems can be regarded to possess a "hidden order" that is not apparent on short length scales. I will describe a variety of different examples of such disordered states of matter that arise in physics, materials science, mathematics and biology. Among other results, I will describe classical ground states that are disordered, hyperuniform and highly degenerate over a wide range of densities up to some critical density, below which the system undergoes a phase transition to ordered states . Disordered hyperuniform systems appear to be endowed with novel physical properties, including complete photonic band gaps comparable in size to those in photonic crystals , improved electronic band-gap properties  and optimal transport properties . Moreover, we have shown that photoreceptor cell patterns in avian retina have evolved to be disordered and hyperuniform .
1. S. Torquato and F. H. Stillinger, "Local Density Fluctuations, Hyperuniform Systems, and Order Metrics," Phys. Rev. E, 68, 041113 (2003).
2. S. Torquato, G. Zhang, and F. H. Stillinger, "Ensemble Theory for Stealthy Hyperuniform Disordered Ground States," Phys. Rev. X, 5,021020 (2015).
3. M. Florescu, S. Torquato and P. J. Steinhardt, "Designer Disordered Materials with Large, Complete Photonic Band Gaps," Proc. Nat. Acad. Sci., 106, 20658 (2009).
4. M. Hejna, P. J. Steinhardt, and S. Torquato, "Nearly Hyperuniform Network Models of Amorphous Silicon, Phys. Rev. B, 87, 245204 (2013).
5. G. Zhang, F. H. Stillinger, and S. Torquato, "Transport, Geometrical, and Topological Properties of Stealthy Disordered Hyperuniform Two-phase Systems," J. Chem. Phys., 145, 244109 (2016).
6. Y. Jiao, T. Lau, H. Haztzikirou, M. Meyer-Hermann, J. C. Corbo, and S. Torquato, Avian Photoreceptor Patterns Represent a Disordered Hyperuniform Solution to a Multiscale Packing Problem, Phys. Rev. E, 89, 022721 (2014).
Bio: Salvatore Torquato is a Professor in Chemistry and the Princeton Institute for the Science and Technology of Materials. He is also affiliated with three other departments: Physics, Applied and Computational Mathematics, and Mechanical and Aerospace Engineering. He has been a Senior Faculty Fellow in the Princeton Center for Theoretical Science. Torquato's research work in theoretical physics is centered in statistical mechanics and soft condensed matter theory. A common theme of his research is the search for unifying and rigorous principles to elucidate a broad range of physical phenomena. His current work focuses on self-assembly theory, disordered and ordered particle packings, liquids, glasses, quasicrystals, crystals, hyperuniform materials, design of materials via inverse optimization techniques, and cancer modeling. He has published 400 journal refereed articles and a book entitled "Random Heterogeneous Materials." Among other awards and honors, he is a Fellow of the American Physical Society (APS), Society for Industrial and Applied Mathematics (SIAM) and American Society of Mechanical Engineers (ASME). He has been the recipient of the ACS Joel Hildebrand Award in Theoretical Chemistry of Liquids, APS David Adler Lectureship Award in Material Physics, SIAM Ralph E. Kleinman Prize, Society of Engineering Science William Prager Medal and ASME Richards Memorial Award. He was a Guggenheim Fellow and was thrice a Member of the Institute for Advanced Study. He recently received a Simons Foundation Fellowship in Theoretical Physics.
Note: Visitors from outside NIST must contact Cathy Graham; (301) 975-3800; at least 24 hours in advance.