The Atomic Scale Design, Control, and Characterization of Oxide Structures IRG is based upon novel chemical, electronic, and magneto-electric phenomena that arise at atomically abrupt complex oxide interfaces. Fundamental understanding of these phenomena and their exploitation to create new classes of devices lies at the heart of the intellectual merit. The broader impacts of the research are in discovering and utilizing novel interfacial phenomena to push devices used for communication, computation, and sensing beyond present paradigms. Three grand challenges motivate the research: designing new interfacial systems that impart unique chemical and physical properties; creating new device paradigms based on the novel properties of complex oxide interfaces; and understanding and manipulating strong electronic correlations that are responsible for many of the novel properties of oxide interfaces. The approach of using cross-cutting teams, including teachers, undergraduates, and high school students to carry out the research, broadens the impact to the entire STEM pipeline.

Nucleic acids (NAs) are extraordinary molecules, developed by life to store and transfer genetic information using sequence-directed duplexing. IRG2 is organized to carry out a broad exploration of the sequence-directed self-assembly of functional materials using Click Nucleic Acids (CNAs). CNAs are a new DNA analog system, invented by Center investigators, in which oligomer chains with DNA-style sequences of selected bases are synthesized using thiol-ene click chemistry. The resulting thio-ether backbone/base structure is similar in its essential geometry to that of DNA and other NA analogs such as peptide nucleic acid (PNA), enabling CNA to exhibit sequence-directed duplexing analogous to that of DNA, as predicted by atomistic molecular dynamic simulations and observed experimentally in complexation, gelation and biodetection studies. The synergistic combination of click chemistry and oligo-nucleotide synthesis has dramatic advantages in expanding sequence-directed assembly into the realm of practical materials science and technology. IRG2 research is organized into two major project areas: Design and Synthesis and Self-Assembly.

•   Design and Synthesis - This project focuses on the creation and characterization of new CNA molecules. Research activities include developing highly scalable synthetic processes for CNAs, expanding the base alphabets, and controlling the backbone and side chains to tailor molecular functionality and compatibility.

•  Self-Assembly - The principal aim of this project is the exploration of CNA sequence-directed self-assembly functionalities in a variety of interfacial and bulk applications, taking advantage of the enhanced programmability and design flexibility afforded by CNAs, in applications including nanotemplating and nanopatterning, nanoparticle organization, block copolymers, and hydrogels.

IRG-1 is investigating materials where spin-orbit coupling (SOC) and electron-electron (Coulomb) correlations are of comparable magnitude, and the subsequent emergence of novel electronic phases in those materials. Using chemistry, structure, epitaxial strain and d-electron count, IRG-1 tunes fundamental interactions in 5d based materials to discover new phases and give insight into their novel properties. Among the remarkable new phases that can arise are axion insulators (predicted to possess unusual magnetoelectric properties) and Weyl semimetals (predicted to have disconnected “Fermi arcs” on the surface of the material). IRG-1 is going beyond the widely studied d⁵ iridates to explore d-electron counts from d² to d⁴.

 

IRG-1 Faculty

• Nandini Trivedi, Professor of Physics (Co-leader)
• Patrick Woodward, Professor of Chemistry (Co-leader)
• David McComb, Professor of Materials Science Engineering
• Mohit Randeria, Professor of Physics
• Wolfgang Windl, Professor of Materials Science Engineering
• Fengyuan Yang, Assoc. Professor of Physics
• Rolando Valdes Aguilar, Asst. Professor of Physics
• Adam Kaminski, Asst. Professor of Physics, Iowa State University
• Jiaqiang Yan, Asst. Professor of Materials Science Engineering, University of Tennessee

The Center for the Science and Engineering of Materials (CSEM) at Caltech, established in September of 2000, addresses both research and educational aspects of polymeric, structural, photonic, and ferroelectric materials that will be necessary to solve critical societal needs of the twenty-first century. The Center pioneers a number of exotic and futuristic materials and applications such as liquid metals, responsive gels, and tiny medical sensors.

IRG Senior Participants:
Katja Nowack (Phys, co-leader), Dan Ralph (Phys, co-leader), Robert Buhrman (Appl Phys), Craig Fennie (Appl Phys),  Greg Fuchs (ApplPhys), Eun-Ah Kim (Phys), Kin Fai Mak (Phys), David Muller (ApplPhys), Farhan Rana (ElecE), Jie Shan (Appl Phys). 

Collaborators: Tomas Arias (Cornell), Sol Gruner (Cornell), Darrell Schlom (Cornell). Industrial Collaborators: Qualcomm, Samsung, Western Digital

The goal of our research is to discover, understand, and apply new mechanisms for controlling spins in magnetic devices. This field is important both because it is an area of rapid progress in fundamental materials physics (e.g., Berry phases, topological materials, and other effects of spin-orbit coupling) and because improved spin control can often be applied quickly for technology. We aim to provide the scientific foundations for energy-efficient nonvolatile memories with revolutionary capabilities and also frequency-agile nanoscale microwave oscillators extendable to THz frequencies.

 

The study and application of LCs stands as a central discipline of soft materials science, providing the conceptual framework for understanding and describing a wide variety of structural and dynamic behavior. IRG1 research is directed toward the creation, understanding, and application of novel soft materials with liquid crystal organization as an underlying theme, and is organized into three major project areas: Molecular/Macroscopic, Functional Liquid Crystal Assemblies, and Active Soft Interfaces.

•   Molecular/Macroscopic - This project focuses on the discovery of new LC structural paradigms; understanding the molecular origins of the macroscopic characteristics of LC systems; and the synthesis and physical evaluation of new materials designed to exhibit chosen features of LC molecular organization. Liquid crystalline systems investigated include helical nanofilament phases of bent-core LCs, colloidal LCs of inorganic molecular monolayer sheets, topological colloids, and chromonic LCs.

•   Functional Liquid Crystal Assemblies - The ordering and structural features of LC phases can be used to advantage in creating novel assemblies of molecules and other nanoscale objects with specific functionality. Investigations are being carried out on photopolymerized nanoporous room-temperature ionic LCs, active nematics, and nanoDNA LCs.

•  Active Soft Interfaces - A principal goal of this project is to develop and explore novel interfaces that can be used to probe interfacial structure and interactions, and be used to detect chemical environment. Research topics include using LC orientation as a sensitive biosensing tool with visual readout for sequence-selective detection of nucleic acids, using azo-SAMs to explore the photofluidization of glasses, and understanding the interplay of bulk and surface LC order.

Principal Investigators
Howard A. Stone (Mechanical & Aerospace Engineering)
Mikko Haataja (Mechanical & Aerospace Engineering)
Andrej Košmrlj  (Mechanical & Aerospace Engineering)

Seed start and end dates: March 1, 2017 - February 28, 2019

The next-generation materials will involve integration of self-assembly at multiple length scales and the ability to use experiments and theory, including continuum mechanics, physical chemistry, statistical physics, mesoscale modeling approaches and molecular-scale simulations, to understand and design the requisite structure-function relationships. For example, in the biological sciences it has been recognized recently that microphase separation can occur in an organized manner to allow multiphase coexistence, even in the absence of membranes. Furthermore, there are examples in the recent literature highlighting novel physics and structures made possible by manipulating the chemistry, swelling, wrinkling, and folding of thin soft materials. Also, this Seed has recently discovered novel composite structures formed by the wrapping and packing of spherical particles by long flexible fibers. Haataja, Košmrlj, and Stone proposed a Seed project highlighting hierarchical soft components built around strengths in soft materials science and engineering in the Princeton community, which has the potential to initiate a new, unique, and forward-looking IRG. Indeed, this activity led directly to preparation of a new IRG.

SuperSeed-8 Highlights
2019 (a) Phase behavior of multi-component liquid mixtures, (b) Electrostatically-driven spontaneous fiber wrapping

2018:  SuperSeed-8: Engineering of Structured Soft Materials

Principal Investigator
Leslie M. Schoop (Chemistry)

Seed start and end dates: September 1, 2017 - August 31, 2019

This seed will use chemical concepts to predict and synthesize new quantum materials. Research will focus on Dirac and Weyl materials as well as two dimensional magnetic material. With combining chemical concepts such as electron counting and bonding rules with ab initio calculations, this research will identify the best candidates that will then be grown in single crystalline form to investigate the physical properties. For these studies, this seed will work in close collaboration with other groups within the MRSEC.

Publications (also included with IRG-1 publications):

• L. M Schoop, F. Pielnhofer, and B.V Lotsch, “Chemical Principles of Topological Semimetals,” Chem. Mater., 30(10):3155–3176, 2018.
• J. Zhang, Y.-H. Chan, C.-K. Chiu, M.G. Vergniory, L.M. Schoop, A.P Schnyder, “Topological band crossings in hexagonal materials,” Phys. Rev. M, 2:074201, (2018).
• C.P. Weber, L.M. Schoop,, S.P Parkin, R.C. Newby, A. Nateprov, B. Lotsch, B.M. Krishna Mariserla, J.M. Kim, K.M Dani, H.A Bechtel, E. Arushanov, M. Ali, “Directly photoexcited Dirac and Weyl fermions in ZrSiS and NbAs,” Appl. Phys. Lett., 113 (22):221906, (2018).
• M.G. Vergniory, L. Elcoro, F. Orlandi, B. Balke, Y.H. Chan, J. Nus, A.P. Schnyder, and L.M. Schoop, “On the possibility of magnetic Weyl fermions in non-symmorphic compound PtFeSb,”Eur. Phys. J. B, 91:213, (2018).

Addresses light-matter interactions that lead to material properties not accessible in equilibrium. Phases and ordered states accessed via light-induced perturbations to energy landscapes, topological material behavior enabled by optical excitation, and formation of exotic quantum phases are explored to provide new understanding of and control over optically responsive materials. Research advances in this IRG are expected to lead to new understanding of material behavior accessible and controllable using temporally structured light, with potential applications in a broad range of technologies for communications and information processing.

The traditional home for research on materials at the University of Pennsylvania (PENN) is the Laboratory for Research on the Structure of Matter (LRSM). The LRSM is an autonomous entity, with its own building and laboratory space, which was created specifically to foster collaborative, interdisciplinary research on the PENN campus. The LRSM receives funding from PENN and the National Science Foundation (NSF) to support a Materials Research Science and Engineering Center (MRSEC) at PENN. The principal investigator on the NSF grant is Arjun G. Yodh, Director of the LRSM. The MRSEC provides core support for selected Interdisciplinary Research Groups (IRGs) and seed projects to pursue a range of fundamental materials problems, involving collaborations with industry and National Laboratories. In addition, the LRSM is developing new-shared experimental facilities (SEFs) both in-house and at National Laboratories. The LRSM is also helping to sustain SEFs that are vital tools for the local materials research community. The LRSM maintains a broad range of innovative educational outreach activities to the materials community, local colleges, and high schools. The LRSM runs a vigorous summer Research Experience for Undergraduates (REU) program, with a special emphasis on participation by women and under-represented groups.