Seminar for the MURI collaboration on Hyperuniformity
Date:
Title: Structural and Physical Properties of Ultradense Disordered Stealthy Hyperuniform Packings
Abstract: Stealthy hyperuniform (SHU) many-particle systems are distinguished by a structure factor that vanishes not only at zero wavenumber (as in ``standard’’ hyperuniform systems) but across an extended range of wavenumbers near the origin. We generate disordered SHU packings of identical spheres using a modified collective-coordinate optimization algorithm that incorporates a soft-core repulsion between particles in addition to the standard stealthy pair potential [J. Kim and S. Torquato, PNAS,117, (2020)]. Compared to the SHU systems without soft-core repulsions, such SHU packings exhibit significantly higher packing fractions, spanning a broad spectrum of structures depending on the stealthiness parameter $\chi$. Here we examine the physical properties of two-phase composites having such dense SHU packings as one of the phases in two and three dimensions, including their effective dynamic dielectric constant and time-dependent diffusive spreadability. We analyze systems of varying sizes, stealthiness parameters ($\chi$), and volume fractions ($\phi$) of the soft-core repulsion. We show that two-phase media obtained from such dense SHU packings display faster interphase diffusion, as a consequence of the higher packing fractions achievable. Moreover, for the same values of the packing fraction, the microstructural arrangement obtained with soft-core repulsion provides faster interphase diffusion. The imaginary part of the effective dynamic dielectric constant of SHU packings vanishes for small wavenumber, implying perfect transparency for the corresponding wavevectors. A larger packing fraction corresponds to a smaller transparency interval, but, as we show, it also displays a smaller absorption peak. Our results demonstrate that disordered SHU packings with soft-core repulsion exhibit advantageous transport and optical behaviors of both theoretical and experimental significance.