| Affiliation: | 1. Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, 48109 USA;2. Carl Zeiss Microscopy Inc., Pleasanton, CA, 94588 USA;3. Carl Zeiss Microscopy GmbH, Oberkochen, 73447 Germany;4. Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang, 110819 China;5. Department of Materials Science & Engineering, University of Michigan, Ann Arbor, MI, 48109 USA;6. https://orcid.org/0000-0002-0501-6998;7. Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720 USAE‐mail: ,;8. Department of Materials Science & Engineering, University of Michigan, Ann Arbor, MI, 48109 USAE‐mail: , |
| Abstract: | A method for the solidification of metallic alloys involving spiral self‐organization is presented as a new strategy for producing large‐area chiral patterns with emergent structural and optical properties, with attention to the underlying mechanism and dynamics. This study reports the discovery of a new growth mode for metastable, two‐phase spiral patterns from a liquid metal. Crystallization proceeds via a non‐classical, two‐step pathway consisting of the initial formation of a polytetrahedral seed crystal, followed by ordering of two solid phases that nucleate heterogeneously on the seed and grow in a strongly coupled fashion. Crystallographic defects within the seed provide a template for spiral self‐organization. These observations demonstrate the ubiquity of defect‐mediated growth in multi‐phase materials and establish a pathway toward bottom‐up synthesis of chiral materials with an inter‐phase spacing comparable to the wavelength of infrared light. Given that liquids often possess polytetrahedral short‐range order, our results are applicable to many systems undergoing multi‐step crystallization. |
