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 H2 and D2 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.