Quantum Interference and
Coherent Control in Junctions
Single molecules are promising candidates for integration into nanoscale devices. Based on the versatility in structural, electronic, optical, and mechanical properties of molecules, molecular devices can be carefully designed and controlled. The small size of molecules implies the necessity of quantum mechanical treatment, and naturally poses questions on the role of coherences in the response properties of molecular devices. In molecular junctions experimental observations were attributed to interference effects in intramolecular electron transfer and elastic transport through single molecules, or to vibrationally induced decoherence.
We model effects of quantum interference on charge and energy transport in molecular junctions, which either can be detected in the measurable transport characteristics or allow to control the molecular device. In particular, we considered optically driven donor-bridge-acceptor junctions, where a possibility for laser-controlled charge-energy separation in multi-terminal molecular junctions was demonstrated. This possibility is a prerequisite for engineering low-heating stable nanoscale devices.
Another direction in the research is related to revealing cooperative effects in transport characteristics of junctions, where we found that peak heights in the inelastic electronic tunneling spectrum (IETS) may be affected by such cooperative effects even when direct intermolecular interactions can be disregarded.
Finally, we proposed a possibility of a pump-probe type of experiments in molecular junctions. While pump-probe spectroscopy is well known and widely used methodology for characterization of molecules in gas phase and on surfaces, slow response of electronic components in junctions limits direct applicability of pump-probe type spectroscopy in assessing the intra-molecular dynamics. We proposed a time averaged dc noise measurements as a signal capable of providing information on intra-molecular dynamics similar to that obtained in the standard pump-probe techniques, thus devising a completely new powerful tool to characterize time-dependent and transient characteristics of molecular junctions.
Representative publications:
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M.A. Ochoa, Y. Selzer, U. Peskin, and M. Galperin. Pump-Probe Noise Spectroscopy of Molecular Junctions. J. Phys. Chem. Lett. 6, 470-476 (2015) [ACS LiveSlides].
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A.J. White, U. Peskin, and M. Galperin. Coherence in charge and Energy Transfer in Molecular Junctions. Phys. Rev. B 88, 205424 (2013).
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M.Galperin and A. Nitzan. Cooperative Effects in Inelastic Tunneling. J. Phys. Chem. B 117, 4449-4453 (2013).
U. Peskin and M. Galperin. Coherently Controlled Molecular Junctions. J. Chem. Phys. 136, 044107 (2012).
