Low conductance of the nickel atomic junctions in hydrogen atmosphere

TL;DR

This study investigates the low electrical conductance of nickel atomic junctions in hydrogen atmospheres using advanced theoretical methods, revealing how hydrogen molecules and atoms influence conductance and spin polarization.

Contribution

It provides detailed first-principles insights into how hydrogen molecules and atoms affect the conductance and spin properties of nickel atomic junctions.

Findings

Ni junction with H2 molecule has ~0.7 G0 conductance due to anti-bonding states.

Ni junction with two H atoms has ~1 G0 conductance, weakly spin-polarized.

Spin-up channels dominate at small junction gaps, spin-down at larger gaps.

Abstract

The low conductance of nickel atomic junctions in the hydrogen environment is studied using the nonequilibrium Green's function theory combined with first-principles calculations. The Ni junction bridged by a $H_2$ molecule has a conductance of approximately 0.7 $G_0$. This conductance is contributed by the anti-bonding state of the $H_2$ molecule, which forms a bonding state with the $3d$ orbitals of the nearby Ni atoms. In contrast, the Ni junction bridged by the two single H atoms has a conductance of approximately 1 $G_0$, which is weakly spin-polarized. The spin-up channels were found to contribute mostly to the conductance at a small junction gap, while the spin-down channels play a dominant role at a larger junction gap.