Charles University, Prague
We study [1] the effects of vibrational degrees of freedom in nanojunctions on the electronic current (shot) noise presently being addressed in ongoing experiments on atomic wires and molecules [2]. Working in the experimentally relevant limit of weak electron-vibronic coupling and using the extended non-equilibrium Green's function formalism with counting field [3, 4] we evaluate the inelastic contribution to the current noise for generic junctions [1], thus extending previous studies addressing only the mean current [5, 6, 7]. The result consists of combinations of terms specific for a given junction and expressed via its structural properties, which can be calculated with, e.g., state-of-the- art ab-initio techniques, and universal, i.e., junction-independent, analytical functions of vibration frequency, voltage, and temperature. We also discuss effects of non-equilibrium phonon occupation (heating), their proper theoretical description within the presented formalism, and their physical relevance and interpretation [8]. Finally, we briefly comment on the connection of our theoretical predictions with the preliminary (unpublished) experimental findings.
[1] F. Haupt, T. Novotný, and W. Belzig, Phys. Rev. Lett. 103, 136601 (2009); Phys. Rev. B 82, 165441 (2010).
[2] D. Djukic and J. M. van Ruitenbeek, Nano Letters 6, 789 (2006); M. Kumar, O. Tal, R. H. Smit, and J. M. van Ruitenbeek, arXiv:1101.3939 (2011).
[3] Yu. V. Nazarov, Ann. Phys. 8, 507 (1999); Quantum Noise in Mesoscopic Physics, Yu. V. Nazarov ed., Berlin: Springer (2003).
[4] A. O. Gogolin and A. Komnik, Phys. Rev. B 73, 195301 (2006).
[5] M. Paulsson, T. Frederiksen, and M. Brandbyge, Phys. Rev. B 72, 201101(R) (2005); T. Frederiksen et al., Phys. Rev. B 75, 205413 (2007).
[6] J. K. Viljas et al., Phys. Rev. B 72, 245415 (2005).
[7] L. de la Vega et al., Phys. Rev. B 73, 075428 (2006).
[8] T. Novotný, F. Haupt, and W. Belzig, arXiv:1105.3912.