Mechanically controlled tunneling of a single atomic defect

This letter reports experiments on the conductance of mesoscopic Bi lms which are polycrystalline and contain single atomic two-level tunneling systems. These defects act as electron scattering centers and give rise to random telegraph signals in the conductance. External strain, applied to the samples at low temperatures, changes the asymmetry energy of the double-well potential of the tunneling particle and thus controls its average dwell time in either well. The measurements allow to determine in a direct way the deformation potential of a particular tunneling defect.