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Science 22 February 2008:
Vol. 319. no. 5866, pp. 1056 - 1060
DOI: 10.1126/science.1146556
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Review

Nuclear Coupling and Polarization in Molecular Transport Junctions: Beyond Tunneling to Function

Michael Galperin,1 Mark A. Ratner,1 Abraham Nitzan,2 Alessandro Troisi3

Much current experimental research on transport in molecular junctions focuses on finite voltages, where substantial polarization-induced nonlinearities may result in technologically relevant device-type responses. Because molecules have strong polarization responses to changing charge state or external field, molecules isolated between electrodes can show strongly nonlinear current-voltage responses. For small applied voltages (up to ~0.3 volt), weak interaction between transporting electrons and molecular vibrations provides the basis for inelastic electron tunneling spectroscopy. At higher voltages and for certain time scale regimes, strong coupling effects occur, including Coulomb blockade, negative differential resistance, dynamical switching and switching noise, current hysteresis, heating, and chemical reactions. We discuss a general picture for such phenomena that arise from charging, strong correlation, and polarization (electronic and vibrational) effects in the molecule and at the interface.

1 Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
2 Department of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
3 Department of Chemistry and Centre of Scientific Computing, University of Warwick, CV4 7AL Coventry, UK.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)