1. Shot Noise and conductance spectroscopy on a single molecule junction Oren Tal Michael Krieger, Rik Hortensius, Bas Leerink Robert Thijssen, Darko Djukic and Jan van Ruitenbeek Leiden University,Netherlands Capri Spring School 2007

2. Electron-Vibration Interaction Inelastic Electron Tunneling Spectroscopy Typically low conductance ~10 -5 G 0 Djukic et al. Phys. Rev. B (R). 71 (2005), 161402 Thygesen et al. Phys. Rev. Lett. 94 (2005), 036807 Point Contact Spectroscopy Typically high conductance ~1G 0 C2H2C2H2 Stipe et al. Rev. Sci. Inst.70 (1999), 137 H2H2

3. Conductance curves of different molecular junctions Step up Step down

4. “step up” to “step down” shape transition as a function of conductance

5. Step size and direction in conductance curves L. de la Vega, A. Martín-Rodero, N. Agraït, and A. Levy Yeyati, PRB 73, 075428 (2006) Low Transmission High Transmission (M. Paulsson et al. PRB 72, 201101R (2005) similar 0.5 transition )

6. Deviation from a single channel model Single channel model: transition between “step up” to “step down” at Do we have more then a single transmission channel for a Pt-H 2 O -Pt junction? Shot Noise measurements In our experiment: transition between “step up” to “step down” at

7. Shot noise in point contacts τ1τ1 τiτi …

8. Shot noise in Pt+H 2 O single molecule junction 6 The transition between to occurs above At the main transmission channel has

9. Conclusions Point contact spectroscopy : The effect of electron - vibration interactions on the differential conductance is inverted at a certain conductance. Shot noise measurements: More than a single transmission channel through the Pt-H 2 O-Pt junction Using the combination of point contact spectroscopy and shot noise measurements the apparent deviation from the relevant models could be resolved. Open question: what is the role of transmission channel mixing due to electron – vibration interactions?

10. Acknowledgments Prof. Jan van Ruitenbeek Michael Krieger Rik Hortensius Bas Leerink Robert Thijssen Darko Djukic Christian Martin Sander Otte Ruud van Egmond Bert Crama

11. Electron-Phonon Interaction V dI/dV 0V Point Contact Spectroscopy Typically high transmission probability V dI/dV 0V Inelastic Electron Tunneling Spectroscopy Typically low transmission probability eV R E k E e e

12. Shot noise in point contacts Lock-in I-V Spectrum Analyser 100 1000 100M Faraday cage dipstick PC cryostat battery S1S1 S2S2

13. Shot noise in Pt+H 2 O single molecule junction 6 At about G=0.5G 0 the main transmission channel has The transition between to occurs above

14. “ Elastic” and inelastic contributions 6 J. K. Viljan et al. PRB 72, 245415 (2005)

15. Conductance histograms: Pt

16. Conductance histograms: Pt+H 2 O >at lower bias voltages lower peaks are more pronounced.

17. Conductance traces >Pt-H 2 O-Pt configurations with higher conductance then 1G 0 (?)