Effects of isotope substitution on local heating and inelastic current in hydrogen molecular junctions

Using first-principles approaches, we investigate the inelastic features in the hydrogen molecular junction. We observe that local heating and inelastic current have significant isotope-substitution effects. The junction instability is also relevant to the isotope substitution. We predict that the HD junction has the smallest breakdown voltage compared with the H-2 and D-2 junction in the optimized geometry. The selection rule for modes that significantly contribute to the inelastic effects is related to the component of vibration along the direction of electron transport.