Tamar Seideman of Northwestern University is supported by an award from the Theory Models and Computational Method program for developing a new approach to coherent control of both electric transport and vibrational dynamics in molecular junctions. The approach is based on semiconductor molecular electronics and the application of low-frequency, sub-bandgap light.
This project focuses on theory and computational realizations of electronic transport in nanodevices and coherent control. The present formalism consistently accounts for the electron scattering dynamics, the possibility of nuclear dynamics, the nonadiabatic coupling of the electronic and vibrational motions, the interaction with light, the plasmonic response of the electrodes, and the dissipation due to electron hole pair excitation and to electrode phonons. Additionally, a novel numerical method is developed for computing the transport properties of molecular junctions. This method is applicable to semiconductor-based junctions and is efficient enough to be implemented in a control scheme. Among the applications to be addressed with theoretical and computational emphases are transport, dynamics, plasmonic response in Au-C60-Au junctions, STM driven surface nanochemistry, and nanoplasmonics. Most of these developments are complementary to forefront research in three collaborative experimental groups. This type of collaboration enhances the education and research experience of students in both theoretical and experimental groups.
Broader impacts result from the continued engagement of this group in a variety of outreach and teaching activities, including work within the National Center for Learning and Teaching in the nanosciences (NCLT), the Network for Computational Nanotechnology (NCN), the Summer Research Opportunities Program for minority undergraduate students (SROP), the Research Experience for Undergraduates and for Teachers Programs (REU and RET, respectively); work within a program that uses science to create collaboration and friendship between Israeli and Palestinian students; advising and mentoring in two international student exchange programs; guidance of several undergraduate students; and delivery of lectures about nanotechnology to the elderly and to children. Furthermore, the numerical code is made available to the scientific community and is broadly disseminated.
Our research was motivated by recent technological achievements that call for new approaches to enable the continuation of device miniaturization and by advancement of fabrication methods to make molecular-scale devices. Molecular-scale optoelectronics, in particular, are needed in order to allow fast functionalities and are now becoming accessible to laboratory experiments. Together, these advances call for theoretical and numerical research to better understand, control and utilize optically-addressed molecular-scale electronics. One goal that the present research accomplished is the development of theories and associated numerical methods to trigger and control molecular-scale electronics with coherent light – a challenge since the metal electrodes absorb the incident light with vastly greater probability than the molecular moiety of the device. Another goal is the application of these methods in collaborative research with experimental colleagues. A third is usage of the research to assist the careers of students and postdoctoral fellows who will be tomorrow’s scientists. A forth is its use to assist our outreach programs and international activities so as to enhance research in the nanosciences by diversification of the scientific community. These accomplishments contribute to a worldwide effort to advance molecular electronics with new functionalities, potentially leading to novel components such as detectors, switches, transistors and logic gates, with anticipate benefit to our health, education, economy, and security.
