Berlin 2018 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 65: Granular Matter / Contact Dynamics (joint session DY/CPP)

CPP 65.5: Talk

Thursday, March 15, 2018, 11:00–11:15, BH-N 333

Optical Properties of Granular Matter — Dominik Kiese, Koray Önder, Sebastian Pitikaris, Matthias Sperl, and •Philip Born — Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, 51147 Köln, Deutschland

Dense packings of hard spheres exhibit strong local ordering, even with lacking long-range order. The point pattern associated with the short-range order of hard sphere packings are shown to exhibit a photonic band-gap, i.e. a complete suppression of wave propagation for wavelengths similar to the center-to-center particle distance [1]. Common center-to-center distances in real granular media are millimetric, and suppression of THz waves reminiscent of development of a photonic bandgap have been observed [2]. We present an experimental study on the evolution of this bandgap with manipulating the structural order in granular packings. Local order in sedimented particle packings is controlled by mixing ratio and size ratio in binary packings. The relation among the bandgap and the structure offers a tool quickly quantify local order and to track structural changes in agitated granular media. We give an outline how to compute the band structure of hard-sphere packings taking into account the full spatial distribution of the dielectric constant.

[1]L. S. Froufe-Pérez et al., Physical Review Letters 117, 053902 (2016).

[2] P. Born. K. Holldack, Review of Scientific Instruments 88, 051802 (2017).