Elucidating Interplays of Chirality and Spin in Chiral Assemblies
Abstract
Research problem- The Chirality-Induced Spin Selectivity (CISS) effect is an intriguing quantum effect that can convert between two different properties of the electron, its charge and spin. This effect stems from the chirality of certain materials, where their structural nature represents a unique handedness which cannot be superimposed onto similar materials with the opposite handedness. CISS provides a strong coupling between spin and charge transport properties in chiral systems without the need for magnetic materials, thereby launching a variety of CISS-related spintronic, chemical, biological, and quantum information applications using different chiral assemblies. However, a large charge-to-spin conversion is intuitively NOT anticipated in organic-based chiral compounds possessing only weak spin-orbit coupling (SOC), but is still frequently observed. Due to the collective phenomena and complex interplay between the structural chirality, electrical and spin properties, and molecular interactions of chiral compounds, a universal description of CISS remains elusive, severely impeding further exploration and exploitation of this fascinating phenomenon. Thus, resolving the paradoxes surrounding the CISS effect is the central objective in this rapidly expanding field. Objective- Our mission is to overcome this long-standing challenge and elucidate the interplay of chirality and spin phenomena in chiral assemblies by 1) exploiting chirality-driven rich interactions between spins, electrons, photons, and phonons in conjugated polymer-based chiral semiconductors and insulators; 2) developing a qualitatively comprehensive CISS model; 3) establishing fundamental structure-property relationships in a variety of synthetically tunable chiral conjugated polymers and their assemblies; 4) extending from fundamental science to demonstration of novel spintronic and bio-inspired device concepts. Approach- This MURI team combines internationally recognized researchers with unique, complementary, and diverse expertise in spin-physics concepts and device engineering (Sun, Hoffmann), polymer synthesis (You), thin-film processing (Diao), thermal transport (Liu), theory-modeling-simulation (Beratan, Zhang), and biomolecular devices (Riehn). Four research thrusts will be established. Thrust 1 will characterize the CISS-driven charge-to-spin interconversion efficiency in chiral polymers and develop a universal CISS model; Thrust 2 will unveil a unique spin-phonon coupling responsible for the CISS effect in chiral insulators; Thrust 3 will utilize state-of-the-art synthesis to establish the structure-property relationships in various chiral assemblies; Thrust 4 will develop CISS devices for spintronic applications and biosensing. Outcome- Our work will lay the foundation for the physical understanding of the CISS effect that remain unsatisfactory, heralding a new paradigm shift in the generation and manipulation of spin information using synthetically tunable polymer compounds. The expansive molecular design space and ease of processing in chiral conjugated polymers provide an ideal platform to develop a universal, and unified model for the CISS effect, enabling us to fully resolve the paradoxes of this emerging field. Our work will rapidly expand the research interests of studying rich interactions between chirality, SOC, spin, and carrier transport properties in chiral materials that possess appealing topological characteristics. Given the promising synergistic convergence of electronic, thermal, and spin properties, we envision that there will be a rapidly growing research interest in CISS-related applications based on chiral polymers and their assemblies. Relevance- This proposed research aligns with the MURI’s mission in addressing grand challenges at the frontier of quantum chiral effects and provides broad relevance across all branches of the DoD.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 29, 2024
- Source ID
- FA95502310311
Entities
People
- Dali Sun
Organizations
- Air Force Office of Scientific Research
- North Carolina State University
- United States Air Force