主持人：Erdal C. Oguz 副研究员

联系人：傅琦 (fuqi@iphy.ac.cn)

Abstract：

Orientational order is typically characterized by a few predefined rotational symmetries. Here, we introduce local ψ(x) and global Ψ(x) orientational order functions defined over a continuous symmetry index x, representing orientational organization as a continuous spectrum rather than isolated modes. Applying this framework across various states of matter reveals crucial physical insights. In this talk we show that in periodic crystals, local and global order coincide perfectly, while in quasicrystals, they differ intrinsically, demonstrating that organization is driven by local angular environments rather than rotational symmetry alone. We also show that in jammed states, while global coherence vanishes, structured local order persists and reveals hidden preferred angular modes. Ultimately, these results show that orientational order is naturally understood as a continuous, geometry-driven spectrum, providing a unified description across crystalline, quasiperiodic, and disordered matter.

Brief CV of Prof. Atahualpa S. Kraemer：

Atahualpa S. Kraemer studied physics at the Faculty of Sciences of the National Autonomous University of Mexico (UNAM), where he also obtained his Ph.D. in Physics under the supervision of David P. Sanders, graduating in 2014. That same year he began his postdoc in Düsseldorf, Germany working in the group of Michael Schmiedeberg, a postdoc that continued in Erlangen, Germany until July 2016. In August 2016 he got a position as an associate professor at UNAM in the area of statistical physics where he currently works. His research areas are colloids, glasses, jammed systems, and quasicrystals. In 2022 he was promoted to full professor, and recently he was nominated for the award "National University Distinction Recognition for Young Academics in the area of Research in Exact Sciences 2023" at UNAM.