Berry-phase effects in transport through single Jahn-Teller molecules

Schultz, Maximilian G.; Nunner, Tamara S.; Oppen, Felix von

doi:10.1103/physrevb.77.075323

Cited by 18 publications

(19 citation statements)

References 22 publications

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“…[21][22][23] But even the simplest rate equation that models a system with just two vibronic levels, q =0,1, and symmetric coupling of the molecule to the electrodes, t L = t R , can show negative differential conductance. Consider, for simplicity, a model with two vibronic states only and generic rates ⌫ qqЈ .…”

Section: A Negative Differential Conductancementioning

confidence: 99%

Nonmonotonic Fano factor and backscattering effects in single-molecule junctions

Schultz

2010

Phys. Rev. B

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Rate equations are a common tool to describe the transport properties of weakly coupled single-molecule junctions. Here, we study the physics of the Anderson-Holstein model at a single vibronic resonance. We derive conditions on the Franck-Condon factors that the resonance increases or decreases the stationary current thus causing negative differential conductance. The role of backscattering of charge at vibronic resonances is also investigated. In strongly asymmetrically coupled devices backscattering causes the resonance to split into two. In symmetrically coupled devices, the Fano factor shows nonmonotonicities, which are related to correlations of forward and backward scattering of charge.

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Section: A Negative Differential Conductancementioning

confidence: 99%

Nonmonotonic Fano factor and backscattering effects in single-molecule junctions

Schultz

2010

Phys. Rev. B

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“…These may show rectifying behavior, 2 dynamical symmetry breaking, 4 and current suppression due to Berry phase effects. 5 Finally, distinctive transport signatures of the breakdown of the BornOppenheimer separation 6 and correlations of vibration and spin properties have been predicted, such as a vibrationinduced spin blockade. 7 Since the complicated transport processes in SMTs may result in a suppression of single-electron tunneling, it becomes more urgent to understand the effect of higher order tunnel processes; even more so since experimentally SMTs typically exhibit a significant tunnel coupling.…”

Section: Introductionmentioning

confidence: 99%

Kinetic equations for transport through single-molecule transistors

2008

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We present explicit kinetic equations for quantum transport through a general molecular quantum dot, accounting for all contributions up to fourth order perturbation theory in the tunneling Hamiltonian and the complete molecular density matrix. Such a full treatment describes not only sequential, cotunneling, and pair tunneling, but also contains terms contributing to renormalization of the molecular resonances as well as their broadening. Due to the latter all terms in the perturbation expansion are automatically well defined for any set of system parameters: no divergences occur and no by-hand regularization is required. Additionally we show that, in contrast to second order perturbation theory, in fourth order it is essential to account for quantum coherence between nondegenerate states, entering the theory through the nondiagonal elements of the density matrix. As a first application, we study a single-molecule transistor coupled to a localized vibrational mode ͑Anderson-Holstein model͒. We find that cotunneling-assisted sequential tunneling processes involving the vibration give rise to current peaks, i.e., negative differential conductance in the Coulomb-blockade regime. Such peaks occur in the crossover to strong electron-vibration coupling, where inelastic cotunneling competes with Franck-Condon suppressed sequential tunneling, and thereby indicate the strength of the electronvibration coupling. The peaks depend sensitively on the coupling to a dissipative bath, thus providing also an experimental probe of the Q factor of the vibrational motion.

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“…Here, the higher dimensional adiabatic potential energy surface of the charged molecule resulting from the coupling to the Jahn-Teller active vibrations leads to distinct transport characteristics. 14,15 Also in this case can a splitting of the degenerate levels result in a qualitatively different signature in the stability diagram. For example, a transport signature characteristic of the pseudo-Jahn-Teller effect might result when the size of the energy splitting matches a multiple of a vibrational energy.…”

Section: Introductionmentioning

confidence: 99%

Image charge effects in single-molecule junctions: Breaking of symmetries and negative-differential resistance in a benzene single-electron transistor

Kaasbjerg

Flensberg

2011

Phys. Rev. B

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Both experiments and theoretical studies have demonstrated that the interaction between the current carrying electrons and the induced polarization charge in single-molecule junctions leads to a strong renormalization of molecular charging energies. However, the effect on electronic excitations and molecular symmetries remain unclear. Using a theoretical framework developed for semiconductor nanostructure based single-electron transistors (SETs), we demonstrate that the image charge interaction breaks the molecular symmetries in a benzene based single-molecule transistor operating in the Coulomb blockade regime. This results in the appearance of a so-called blocking state, which gives rise to negative differential resistance (NDR). We show that the appearance of NDR and its magnitude in the symmetry-broken benzene SET depends in a complicated way on the interplay between the many-body matrix elements, the lead tunnel coupling asymmetry, and the bias polarity. In particular, the current reducing property of the blocking state causing the NDR, is shown to vanish under strongly asymmetric tunnel couplings, when the molecule is coupled stronger to the drain electrode. The calculated IV characteristic may serve as an indicator for image charge broken molecular symmetries in experimental situations.

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Berry-phase effects in transport through single Jahn-Teller molecules

Cited by 18 publications

References 22 publications

Nonmonotonic Fano factor and backscattering effects in single-molecule junctions

Nonmonotonic Fano factor and backscattering effects in single-molecule junctions

Kinetic equations for transport through single-molecule transistors

Image charge effects in single-molecule junctions: Breaking of symmetries and negative-differential resistance in a benzene single-electron transistor

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