Influence of nanomechanical properties on single-electron tunneling: A vibrating single-electron transistor

Abstract

Abstract. -We describe single electron tunneling through molecular structures under the influence of nano-mechanical excitations. We develop a full quantum mechanical model, which includes charging effects and dissipation, and apply it to the vibrating C60 single electron transistor experiment by Park et al. [Nature 407, 57 (2000)]. We find good agreement and argue vibrations to be essential to molecular electronic systems. We propose a mechanism to realize negative differential conductance using local bosonic excitations.Introduction. Experiments on electronic transport through nano-scale systems show a variety of physical conduction mechanisms. Due to their small size quantum mechanics becomes important and Coulomb blockade, interference, and Kondo physics are observed. Molecular systems [1][2][3][4][5][6][7][8] are characterized by large electronic energies beyond room temperature and therefore offer the possibility to measure positions of molecular orbitals by transport spectroscopy. Furthermore, mechanical degrees of freedom in molecules have energies of order 1 − 10 meV which can be probed experimentally for temperatures in the Kelvin regime. This letter addresses the latter topic and combines nano-electronic with nano-mechanical properties, in particular we model the experiment in Ref. [9]. We find that local bosonic excitations have an important influence on single electron tunneling, and thus need to be included in models for molecular electronics. Based on those systems we propose another way to realize negative differential conductance (NDC).Attempts to model transport through molecular nano structures up to now focused more on the electronic structure [10]. In this letter we go one step further and include molecular vibrations (or any other local bosonic excitation) as well. We remark that our approach is fundamentally different from models where the vibration serves as a shuttle for the electrons [11,12]. We address the case where the vibrational frequency is several orders of magnitude larger than the frequency associated with tunneling events. Moreover the physics is dominated

Single-molecule transport in three-terminal devices

“…Inelastic effects in molecular junctions originate from coupling between electronic and nuclear degrees of freedom [57][58][59][60][61][62]. The nuclei are much heavier than the electrons.…”

Self-consistent theory of molecular switching

“…In the strong-coupling regime and for ⌫Ӷ 0 , when the electron-ion interaction energy E p ͑defined below͒ exceeds ប 0 , the physics is governed by the Franck-Condon effect, i.e., when the tunneling of an electron onto the molecule with the simultaneous emission or absorption of several phonons is more probable than elastic tunneling. The current as the function of voltage exhibits steps separated by ប 0 / e, 10,[22][23][24] and the nonequilibrium electronic heating of the molecular vibrational mode leads to self-similar avalanche dynamics of current with the intervals of large current alternating with the periods of strongly suppressed current. 11 In this paper, we study the case of "slow" phonons at strong coupling, ⌫ӷ 0 for eV Ͼប 0 .…”

Counting statistics of tunneling through a single molecule: Effect of distortion and displacement of vibrational potential surface

“…8,9,10,11,12,13,14,15,16,17,18,19,20,21 In particular, electronic transport measurements in suspended Carbon nanotubes have yielded I-V curves demonstrating perfect signatures of phonon-mediated tunneling, e.g. stepwise structures with equal widths in voltage and gradual height reduction by the Franck-Condon (FC) factor.…”