Electronic and Structural Dynamics in Tunable Superatomic Crystals

Purdue University, West Lafayette IN

Investigators

Abstract

With support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program in the Division of Chemistry, Hanzhe Liu of Purdue University is investigating ultrafast electronic and structural dynamics in metal chalcogenide clusters and their assembled superatomic solids. Superatomic solids use atomically precise nanoclusters as building blocks. These materials exhibit widely tunable properties and are promising for optoelectronic and thermoelectric applications. However, the complex chemical compositions of these materials have posed a challenge for understanding the fundamental intra- and inter-molecular interactions within them. To address this challenge, the Liu group uses ultrashort extreme ultraviolet light pulses to observe the real-time electronic and atomic motions in superatomic materials. This technique allows detection of electronic and structural dynamics occurring at individual elements within the superatomic materials and can reveal how macroscopic properties arise from the microscopic molecular interactions. Their discoveries could give insight into the design principles for superatomic solids to be deployed for optoelectronic, catalytic, and thermoelectric applications. This project combines physical chemistry, materials science, and laser technology, offering diverse training opportunities for students participating in this research. Beyond in-lab training, the Liu group is designing lab demonstrations for K-12 communities and undergraduate students. The properties of superatomic crystals can be widely tuned by varying the geometry and chemical composition of the nanoclusters. To understand the chemical origins of macroscopic properties, the Liu group at Purdue University uses ultrafast extreme ultraviolet (XUV) spectroscopy to study the coupled electronic and structural dynamics in superatomic crystals. Ultrafast XUV spectroscopy offers elemental specificity and femtosecond resolution, allowing the decomposition of complex dynamics into the electronic and structural responses occurring at different elements. Through measurements of a series of metal chalcogenide clusters and their assembled superatomic solids with different geometry and chemical compositions, Hanzhe Liu and his group aim to understand the interplay between localized molecular dynamics and long-range collective responses, and how they are responsible for macroscopic material properties. These studies aim to help establish structure-function correlations in superatomic crystals and provide insights into chemical design principles that might be used to develop superatomic materials for optoelectronic applications. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.