R&D: Molecule Co-Discovered at University of Limerick Leads to Breakthrough on How Data Are Stored

From University of Limerick

Scientists at University of Limerick’s Bernal Institute have helped discover a molecule that could have a major impact on how data is stored and processed.

Damien Thompson, associate professor in Physics, UL,
who leads a research team in predictive materials design at Bernal Institute

The UL researchers found that a simple metal–organic molecule can go beyond simple binary (0 – OFF, 1 – ON) computing logic and can in fact switch between three distinct, long-lived states.

This first demonstration of a ternary ‘molecular traffic light’ device could provide a low-energy means of storing and processing unstructured ‘big data’ required for the IoT and Artificial Intelligence (AI).

Damien Thompson, associate professor in Physic, UL, who leads a research team in predictive materials design at the Bernal Institute, proved, using state of the art computer simulations performed on the Irish Centre for High-End Computing supercomputer, that the surprisingly stable third state is made possible by an unequal sharing of electrons between different sides of the molecule.

The research solves a 50-year-old puzzle in physics.

The work, published in the journal Nature Nanotechnology, is a result of an international collaboration with National University of Singapore (NUS), Indian Association for the Cultivation of Science (IACS), and Texas A&M University (TAMU).

The device was conceptualized and developed at NUS by Professor T. Venkatesan and his post-doctoral researcher Dr. Sreetosh Goswami, based on a molecular complex discovered by Prof Sreebrata Goswami of IACS in Kolkata. Prof Stanley Williams, founding director of the Quantum Science Research Laboratory at Hewlett-Packard and now at TAMU, developed the new device paradigm based on the newly discovered electrical properties.

Science Foundation Ireland-supported scientist and theory lead on the project Professor Thompson explained that ‘big data’ is the Achilles heel of next-generation of computing, demanding ever-increasing higher computing density which means, with current binary devices, huge power requirements, impractically complex component manufacture and/or convoluted circuit designs.

“Here, we managed to push way beyond industry roadmaps by finding a ternary resistive memory device with three states that are well-separated from each other in terms of conductance and, just as importantly, stay working away perfectly for weeks on end,” he explained.

“The trick to this first commercially viable multi-level computing device is a slightly arcane physical phenomenon called ‘charge disproportionation’ or symmetry breaking, which we proved using computer simulations,” he added.

Professor Luuk van der Wielen, director, Bernal Institute, said the research was “high impact and reinforces the ambition of the Bernal Institute to impact the world on the basis of top science in an increasingly international context. “

“This is a continuation of Bernal scientists’ world-leading contribution to the field of predictive materials modelling,” he added.

Professor Sean Arkins, Dean, science and engineering, UL, said: “Researchers at UL’s Department of Physics continue to pioneer the exploitation of organic materials for electrical applications, and this work places them at the forefront of molecular nanotechnology.”

Thompson outlined that scientists have long noticed that certain materials can ‘breathe’ in an electric or magnetic field, and sometimes the electron cloud around the molecules can lose its symmetry.

“This has remained an academic curiosity until now lacking technological relevance because it has always been associated with a big change in temperature or pressure,” he said.

“Whereas here the third asymmetric state is created simply by allowing current to flow through the device and it persists over a broad temperature range (-100 to +100 °C) so it is suitable for most conventional computing as well as future applications emerging from the symbiosis between physics, computing and biology.“

“In this new material, ions pulse back and forth between different binding sites on the molecules, which opens up the third state, making it energetically accessible and technologically exploitable,” he added.

Article: Charge disproportionate molecular redox for discrete memristive and memcapacitive switching

Nature Nanotechnology has published an article written by Sreetosh Goswami, NUSNNI-NanoCore, National University of Singapore, Singapore, Singapore, NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore, Singapore, Santi P. Rath, School of Chemical Sciences, Indian Association for the Cultivation of Science (IACS), Kolkata, India, Damien Thompson, Department of Physics, Bernal Institute, University of Limerick, Limerick, Ireland, Svante Hedström, Present address: Svensk Kärnbränslehantering, Solna, Sweden, and Fysikum, Stockholm University, Stockholm, Sweden, Meenakshi Annamalai, NUSNNI-NanoCore, National University of Singapore, Singapore, Singapore, Rajib Pramanick, School of Chemical Sciences, Indian Association for the Cultivation of Science (IACS), Kolkata, India, B. Robert Ilic, Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD, USA, Soumya Sarkar, NUSNNI-NanoCore, National University of Singapore, Singapore, Singapore, and NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore, Singapore, Sonu Hooda, NUSNNI-NanoCore, National University of Singapore, Singapore, Singapore, Christian A. Nijhuis, NUSNNI-NanoCore, National University of Singapore, Singapore, Singapore, Department of Chemistry, National University of Singapore, Singapore, Singapore, and Centre for Advanced 2D Materials, National University of Singapore, Singapore, Singapore, Jens Martin, Present address: Leibniz Institut für Kristallzüchtung, Materials Science Department, Berlin, Germany, NUSNNI-NanoCore, National University of Singapore, Singapore, Singapore, Centre for Advanced 2D Materials, National University of Singapore, Singapore, Singapore, and Department of Physics, National University of Singapore, Singapore, Singapore, R. Stanley Williams, Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX, USA, Sreebrata Goswami, School of Chemical Sciences, Indian Association for the Cultivation of Science (IACS), Kolkata, India, and T. Venkatesan, NUSNNI-NanoCore, National University of Singapore, Singapore, Singapore, NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore, Singapore, Department of Physics, National University of Singapore, Singapore, Singapore, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore, and Materials Science and Engineering Department, National University of Singapore, Singapore, Singapore.

Abstract: “Electronic symmetry breaking by charge disproportionation results in multifaceted changes in the electronic, magnetic and optical properties of a material, triggering ferroelectricity, metal/insulator transition and colossal magnetoresistance. Yet, charge disproportionation lacks technological relevance because it occurs only under specific physical conditions of high or low temperature or high pressure. Here we demonstrate a voltage-triggered charge disproportionation in thin molecular films of a metal–organic complex occurring in ambient conditions. This provides a technologically relevant molecular route for simultaneous realization of a ternary memristor and a binary memcapacitor, scalable down to a device area of 60 nm². Supported by mathematical modelling, our results establish that multiple memristive states can be functionally non-volatile, yet discrete—a combination perceived as theoretically prohibited. Our device could be used as a binary or ternary memristor, a binary memcapacitor or both concomitantly, and unlike the existing ‘continuous state’ memristors, its discrete states are optimal for high-density, ultra-low-energy digital computing.“