Krill Prize 2017
Ben Gurion University
Dr. Yonatan Dubi
Charge and Energy Transport in Molecular devices.
A central focus of my research is the study of energy and electronic transport in molecular devices. The Field of molecular electronics aims at developing molecular-level technologies which will complement – and eventually supersede – current microelectronic technologies. For this aim, it is essential to devise molecular junctions (a single molecule or a molecular layer sandwiched between metallic electrodes) with electronic properties that mimics at least some of the behavior of modern- day components. Achieving this goal requires detailed understanding of the fundamental processes that govern the electronic transport in such molecular junctions, and using this understanding to design functional devices.
We have been studying various effects related to the transport in molecular junctions. A recent example is a model we constructed to describe a DNA-based single-molecule diode. The theory which we developed was compared to the experiments performed at the group of Prof. B. –Q. Xu at the University of Georgia, and allowed us to explain the experimentally observed rectification (diode-like) behavior. The combined experimental-theoretical study has been published in Nature Chemistry (ref. 42). Within the same collaboration with Prof. Xu, we developed a new model for negative-differential-resistance molecular devices (refs. 34 & 38), which explained puzzling experimental results. In addition, we developed a novel theory of transport through self-assembled- monolayer-based (SAM) molecular devices (ref. 35), which was able for the first time to explain important experimental observations, such as reduction of current compared to the single-molecule junctions, molecule-length-dependence of currents, and the odd-even effect.
Another long-standing focus of interest in my group is how energy is distributed in and transferred through molecular junctions. Special focus is given to thermoelectric energy conversion – the conversion of a temperature gradient to electric voltage (e.g., refs. 12, 14-16, 18, 19, reviewed in ref. 21). Recently, we addressed the outstanding question: can a molecular system be designed which will exhibit enhanced thermoelectric performance in realistic conditions? The answer turns out to be “Yes”; we demonstrated that using novel geometries for molecular junctions (helicene- based junctions and hybrid molecule-nanoparticle junctions) one can enhance the thermoelectric performance of realistic systems (refs. 37 & 39).
Exciton transport, open quantum systems and quantum biology
Another important part of my research is the development of new methods for calculating energy transport. Borrowing ideas from the field of open quantum systems, we formulated a quantum master equation that can be used to study thermoelectricity in molecular junctions (refs. 11, 12 & 16). Recently, we extended the formulation to study, for the first time, solar energy conversion (i.e. light-to-electricity) in a quantum molecular photo-cell (ref. 36). This led us to the field which is currently a central focus of the group, namely quantum-coherent exciton transfer in photosynthetic complexes (ref. 40), where we showed that maintaining quantum coherence in model natural photosynthetic complexes leads to enhancement of power output, and provided the detailed mechanism for this enhancement. This is part of the emerging field of quantum biology, where the central question is “are there quantum coherent effects in biological systems, and if so, are they used by nature to enhance performance?”.