Atomic tunneling from a scanning-tunneling or atomic-force microscope tip: dissipative quantum effects from phonons.

We study the effects of phonons on the tunneling of an atom between two surfaces. In contrast to an atom tunneling in the bulk, the phonons couple very strongly and qualitatively change the tunneling behavior. This is the first example of Ohmic coupling from phonons for a two-state system. We propose an experiment in which an atom tunnels from the tip of an scanning-tunneling microscope, and show how its behavior would be similar to the macroscopic quantum coherence behavior predicted for SQUIDs. The ability to tune and calculate many parameters would lead to detailed tests of the standard theories.