DMR-1420634, Center for Precision Assembly of Superstratic and Superatomic Solids (PAS³)

PAS³ consists of two interdisciplinary research groups (IRGs) that assemble new materials from atomically precise building blocks. The IRG research activities were expanded by seed programs, complemented by industry, national lab, and international partnerships, and supported by investments in shared facilities. PAS³ built a robust education and human resources program, and worked to build diversity at all levels. 

Intellectual Merit: Both teams have demonstrated highly interdisciplinary research with pathbreaking results. The work of the IRGs led to 225 refereed publications in top journals such as Science (4 papers), Nature (4), Nature Materials (8), Nature Nanotechnology (6) and JACS (14). 

IRG1, Heterostructures of van der Waals Materials, created new materials by assembling two-dimensional (2D) materials into layered van der Waals Heterostructures (vdWH) whose properties can be controlled by composition, thickness, and rotation of the layers.  The IRG1 team addressed fundamental materials science challenges for vdWH:

1. Synthesis and characterization of ultra-pure materials. These include: 2D semiconductors with 1000? lower defect density; topological insulators (TIs) with precisely controlled doping and new magnetic layered superlattices. 
2. Breakthroughs in materials assembly, manipulation, and electrical contacts.  The team built equipment for assembly of air-sensitive materials; demonstrated tuning of vdWH properties by rotating layers; and developed a new approaches for achieving electrical contact to 2D materials.  
3. Exploration of Novel Phenomena: Using high-purity semiconductors, the team developed new understanding of their optical response and energy levels that emerge in magnetic fields. The team uncovered fundamental properties of 2D superconductivity and found a new tunable 2D superconductor.  A major breakthrough was discovery of quantized energy levels in magnetically doped topological insulators without an applied magnetic field.

IRG2, Superatom Assembled Solids, assembled chemically precise clusters (?superatoms?) into crystals with varied compositions, structures and dimensionality. The team demonstrated that unique collective behaviors and phase transitions emerge in such materials as a result of their atomic precision. 

1. Synthesis:  The IRG2 team synthesized superatoms and created superatomic solid solutions with tunable properties.  The IRG2 team developed the chemistry to covalently connect superatoms, and used electrocrystallization to create a remarkable woven structure. Stable semiconducting materials were achieved by high-temperature fusion of superatoms.  
2. Dimensionality: The IRG2 team created 2D layered superatomic crystals by polymerizing superatoms. High-temperature synthesis yielded exciting new 2D layered materials, including band semiconductors and a novel magnetic semiconductor. 
3. Materials Properties: The IRG2 team studied superatom junctions capable of processing integer units of charge, and showed ?decoupling? of thermal from electrical transport in thin films. Optical studies revealed a hierarchy of vibrational modes in superatom solids. The team pioneered a new diffraction-based technique to map electron distribution, and demonstrated a superatomic crystal with switchable optical, electrical and magnetic properties. Finally, the team demonstrated the first superatomic superconductor.  

The PAS³ Seed Program brought 7 new faculty participants into the existing IRGs, and a SuperSeed project explored novel approaches to networks of single-photon quantum emitters. The seed program has also supported an effort with Fashion Institute of Technology on new bio-materials for textiles. 

Broader Impacts:  PAS³ served as an interdisciplinary training ground for the next generation of scientists. Each IRG was led by two postdoctoral Fellows, and a student-postdoc leadership council helped to set educational priorities. 45 PhD students and 28 postdocs were supported by the center.

The materials investigated by PAS³ have broad potential applications in electronics, opto-electronics, and energy. Honda and Rassini sponsored work by PAS³ researchers to explore applications of these materials, and a start-up company on battery storage was launched by IRG2 researchers. The seed program on bio-based textiles addressed a critical source of pollution, and generated broad public visibility.

PAS³ implemented a broad Education and Human Resources strategy to improve STEM and materials education at all levels. The PAS³ summer research program brought undergraduate, community college, and high school students to our labs. An annual ?March Materials Madness? event reached elementary school students, and a ?PhD-for-a-day? program worked with middle schools.  PAS³ partnered with the Cornell MRSEC on workshops for local STEM teachers.

PAS³ worked to build Diversity at all levels. Partners CCNY, Barnard, and FIT serve diverse student populations, and a new partnership with Howard University was initiated in 2019. Diversity was enhanced by international partnerships with University of the Virgin Islands, the University of the West Indies, and others.  PAS³ worked with its partners to diversify its undergraduate research programs and improve diversity in the PhD programs.  Diversity at the PhD level has exceeded the baseline at Columbia, with 14 female/6 URM out of 45 graduated. PAS³ has also supported 4 students in Columbia?s Bridge-to-PhD program. 

Last Modified: 02/02/2022
Modified by: James C Hone