  The electric conductance of Rh atomic contacts was investigated under the
electrochemical potential control. The conductance histogram of Rh atomic
contacts varied with the electrochemical potential. When the electrochemical
potential of the contact was kept at $\Phi_{0}$= 0.1 V vs. Ag/AgCl (Rh
potential), the conductance histogram did not show any features. At $\Phi_{0}$=
-0.1 V (under potential deposited hydrogen potential), the conductance
histogram showed a feature around 2.3 $G_{0}$ ($G_{0}$ =2$e^{2}/h$), which
agreed with the conductance value of a clean Rh atomic contact, which was
observed in ultrahigh vacuum at low temperature. At $\Phi_{0}$= -0.25 V (over
potential deposited hydrogen potential), the conductance histogram showed
features around 0.3 and 1.0 $G_{0}$. The conductance behavior of the Rh atomic
contact was discussed by comparing previously reported results of other metals,
Au, Ag, Cu, Pt, Pd, Ni, Co, and Fe. The conductance behavior of the metal
atomic contacts related with the strength of the interaction between hydrogen
and metal surface.
