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Effect of phonons on the ac conductance of molecular junctions.

Ueda A, Entin-Wohlman O, Aharony A - Nanoscale Res Lett (2011)

Bottom Line: We theoretically examine the effect of a single phonon mode on the structure of the frequency dependence of the ac conductance of molecular junctions, in the linear response regime.The conductance is enhanced (suppressed) by the electron-phonon interaction when the chemical potential is below (above) the energy of the electronic state on the molecule.PACS numbers: 71.38.-k, 73.21.La, 73.23.-b.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Ben Gurion University, Beer Sheva 84105, Israel. akiko@bgu.ac.il.

ABSTRACT
We theoretically examine the effect of a single phonon mode on the structure of the frequency dependence of the ac conductance of molecular junctions, in the linear response regime. The conductance is enhanced (suppressed) by the electron-phonon interaction when the chemical potential is below (above) the energy of the electronic state on the molecule.PACS numbers: 71.38.-k, 73.21.La, 73.23.-b.

No MeSH data available.


Related in: MedlinePlus

The ac conductance as a function of the ac frequency ω at ε0 - μ = Γ. (a) The total conductance when ΓL = ΓR and δμL = -δμR. The broken lines indicate the conductance in the presence of e-ph interaction with γ = 0.4Γ. ω0 = 2Γ, or 0.5Γ. The solid line is the 'bare' conductance G0, in the absence of e-ph interaction. (b) The additional conductance due to the e-ph interaction, Gint(ω) = GH(ω) + Gex(ω), for the same parameters as in (a).
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Figure 2: The ac conductance as a function of the ac frequency ω at ε0 - μ = Γ. (a) The total conductance when ΓL = ΓR and δμL = -δμR. The broken lines indicate the conductance in the presence of e-ph interaction with γ = 0.4Γ. ω0 = 2Γ, or 0.5Γ. The solid line is the 'bare' conductance G0, in the absence of e-ph interaction. (b) The additional conductance due to the e-ph interaction, Gint(ω) = GH(ω) + Gex(ω), for the same parameters as in (a).

Mentions: Next, Figure 2a shows the full ac conductance G as a function of the ac frequency ω, when ε0 - μ = Γ. The solid line in Figure 2a indicates G0. Two broad peaks appear around ω of order ± 1.5(ε0 - μ). The broken lines show G in the presence of the e-ph interaction with ω0 = 2Γ, ω0 = Γ, or ω0 = 0.5Γ. The e-ph interaction increases the conductance in the region between the original peaks, shifting these peaks to lower /ω/, and decreases it slightly outside this region. Figure 2b indicates the additional conductance due to the e-ph interaction, Gint, for the same parameters. Similar results arise for all positive ε0 - μ. Both GH and Gex show two sharp peaks around ω ~ ± (ε0 - μ) (causing the increase in G and the shift in its peaks), and both decay rather fast outside this region. In addition, Gex also exhibits two negative minima, which generate small 'shoulders' in the total G. For ε0 >μ, Gint is dominated by Gex. The exchange term virtually creates a polaron level in the molecule, which enhances the conductance. The amount of increase is more dominant for lower ω0. The situation reverses for ε0 <μ, as seen in Figure 3. Here, G0 remains as before, but the ac conductance is suppressed by the e-ph interaction. Now Gint is always negative, and is dominated by GH. The Hartree term of the e-ph interaction shifts the energy level in the molecule to lower values, resulting in the suppression of G. The amount of decrease is larger for lower ω0.


Effect of phonons on the ac conductance of molecular junctions.

Ueda A, Entin-Wohlman O, Aharony A - Nanoscale Res Lett (2011)

The ac conductance as a function of the ac frequency ω at ε0 - μ = Γ. (a) The total conductance when ΓL = ΓR and δμL = -δμR. The broken lines indicate the conductance in the presence of e-ph interaction with γ = 0.4Γ. ω0 = 2Γ, or 0.5Γ. The solid line is the 'bare' conductance G0, in the absence of e-ph interaction. (b) The additional conductance due to the e-ph interaction, Gint(ω) = GH(ω) + Gex(ω), for the same parameters as in (a).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211260&req=5

Figure 2: The ac conductance as a function of the ac frequency ω at ε0 - μ = Γ. (a) The total conductance when ΓL = ΓR and δμL = -δμR. The broken lines indicate the conductance in the presence of e-ph interaction with γ = 0.4Γ. ω0 = 2Γ, or 0.5Γ. The solid line is the 'bare' conductance G0, in the absence of e-ph interaction. (b) The additional conductance due to the e-ph interaction, Gint(ω) = GH(ω) + Gex(ω), for the same parameters as in (a).
Mentions: Next, Figure 2a shows the full ac conductance G as a function of the ac frequency ω, when ε0 - μ = Γ. The solid line in Figure 2a indicates G0. Two broad peaks appear around ω of order ± 1.5(ε0 - μ). The broken lines show G in the presence of the e-ph interaction with ω0 = 2Γ, ω0 = Γ, or ω0 = 0.5Γ. The e-ph interaction increases the conductance in the region between the original peaks, shifting these peaks to lower /ω/, and decreases it slightly outside this region. Figure 2b indicates the additional conductance due to the e-ph interaction, Gint, for the same parameters. Similar results arise for all positive ε0 - μ. Both GH and Gex show two sharp peaks around ω ~ ± (ε0 - μ) (causing the increase in G and the shift in its peaks), and both decay rather fast outside this region. In addition, Gex also exhibits two negative minima, which generate small 'shoulders' in the total G. For ε0 >μ, Gint is dominated by Gex. The exchange term virtually creates a polaron level in the molecule, which enhances the conductance. The amount of increase is more dominant for lower ω0. The situation reverses for ε0 <μ, as seen in Figure 3. Here, G0 remains as before, but the ac conductance is suppressed by the e-ph interaction. Now Gint is always negative, and is dominated by GH. The Hartree term of the e-ph interaction shifts the energy level in the molecule to lower values, resulting in the suppression of G. The amount of decrease is larger for lower ω0.

Bottom Line: We theoretically examine the effect of a single phonon mode on the structure of the frequency dependence of the ac conductance of molecular junctions, in the linear response regime.The conductance is enhanced (suppressed) by the electron-phonon interaction when the chemical potential is below (above) the energy of the electronic state on the molecule.PACS numbers: 71.38.-k, 73.21.La, 73.23.-b.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Ben Gurion University, Beer Sheva 84105, Israel. akiko@bgu.ac.il.

ABSTRACT
We theoretically examine the effect of a single phonon mode on the structure of the frequency dependence of the ac conductance of molecular junctions, in the linear response regime. The conductance is enhanced (suppressed) by the electron-phonon interaction when the chemical potential is below (above) the energy of the electronic state on the molecule.PACS numbers: 71.38.-k, 73.21.La, 73.23.-b.

No MeSH data available.


Related in: MedlinePlus