This paper concerns an experimental and theoretical study of the transition between two consecutive conductance plateaus as obtained in breaking gold contact experiments. The experimental measurements performed at 100K with a scanning tunneling microscope and variable elongation speeds show that the transitions between consecutive plateaus can appear in the conductance traces as an abrupt conductance step, a smooth quasicontinuous change or as large amplitude conductance fluctuations. The theoretical calculations based on a non-orthogonal tight-binding Hamiltonian have shown that for a given deformation there are several structures having close and competing energies. We discuss the relation between the temperature, sampling frequency, stretching speed and energy barriers which can explain the conditions for the observation of the three kinds of conductance traces.
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