Metal-Phthalocyanine Superlattices: Exploring Quantum Devices as a New Paradigm for Sensing Applications and Information Storage

Alexander Baker | 19-LW-028

Project Overview

Phthalocyanines are organic semiconductor molecules that can form well-ordered films, with applications in chemical sensing and more recently in templating one-dimensional, transition-metal nanowires. These materials provide a fertile ground for innovation in material physics, using ideas beyond conventional tunnel junctions or spin valves to develop new spintronic memory, logic, and/or sensing devices.

Metal-phthalocyanine superlattices use interfaces between different magnetic/non-magnetic metal centers in one-dimensional chains to enable tunable band structures and electronic properties. This project used element-specific, x-ray absorption spectroscopy to examine how chain termination and length affects the magnetic properties of such superlattices, revealing profound effects of hybridization on magnetic coercivity. Coupled with structural characterization and theoretical efforts by academic collaborators, we developed a new model for magnetic reversal in such structures. Further measurements also discovered unexpected decoupling of quantum mechanical components of magnetism in certain cases. Over the course of the project, the ability to tune and control their properties was demonstrated, and an improved understanding of their magnetism and electronic structure was developed. Due to the low temperatures required for magnetism, this aspect of the work is primarily applicable to quantum computing, and indeed long coherence times have been shown in other phthalocyanine systems.

Mission Impact

The materials and structures studied in this project represent cutting-edge condensed matter physics research that seeks to provide new ideas for sensing or computing operations. This work supports Lawrence Livermore National Laboratory’s research challenges in physics, chemistry, and materials science. Gas sensing is an attractive application for phthalocyanines, and the ability to modify bonding and energy levels using superlattices could allow greater sensitivity or discrimination of adsorbed molecules. This research has potential applications in the Laboratory's defense mission. In addition, the project supports the Laboratory's mission research challenge in quantum science and technology.

Publications, Presentations, and Patents

Baker, A., et al. 2019. "Magnetic Spectroscopy of 1-D Iron Chains," Magnetism and Magnetic Materials Conference, Las Vegas, NV, November 2019. LLNL-PRES-795817

Cable, M. and A. Baker. 2019. "Characterization of Metal-phthalocyanines for use in Sensing and Quantum Computing," 2019 Summer Student Poster Symposium, Lawrence Livermore National Laboratory, Livermore, CA. LLNL-POST-783863

Vargas, N., et al. 2020. "Helical Spin Structure in Iron Chains with Hybridized Boundaries," Applied Physics Letters, 117, 213105. doi:10.1063/5.0022926. LLNL-JRNL-76828