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Q: Quantenoptik und Photonik

Q 40: Laserspektroskopie

Q 40.3: Talk

Thursday, March 25, 2004, 17:00–17:15, HS 204

Interaction of a single molecule with sharp metal tips at low temperature — •Senta Karotke and Bert Hecht — Nano-Optics group, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel

A very interesting topic, which becomes accessible experimentally, is the examination of the properties of single quantum systems like single molecules and their interactions.

Single molecules at cryogenic temperature are very sensitive probes for optical and electrical processes in their local environment. For example, the resonance of a molecule in the vicinity of a sharp metal tip is shifted. This shift occures either due to the interaction of the molecule with its backreflected field or, if a voltage is applied to the tip, due to the Stark effect. This fact can be exploited for high-resolution localization and imaging of single molecules or other quantum systems.

The experimental investigations are carried out by using the well-established technique of a confocal microscope which is combined with a newly developed scanning tip setup with a tuning fork shearforce gapwidth control. In the temperature range from RT down to cryogenic T, we are able to record topographic images as well as optical images. We will present results showing tip-induced Stark effect of a single molecules, i.e. the frequency shift of single molecules as a function of the tip position. This demonstrates a new powerful technique of resolving single molecules with a spatial resolution only limited by the characteristic size of the tip.