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Register a new userSingle channel conductance of H$_2$ molecules attached to platinum or palladium electrodes
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Added by
V\\'ictor Manuel Garc\\'ia Su\\'arez
Publication date
2004
fields
Physics
and research's language is
English
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We report a detailed theoretical study of the bonding and conduction properties of an hydrogen molecule joining either platinum or palladium electrodes. We show that an atomic arrangement where the molecule is placed perpendicular to the electrodes is unstable for all distances between electrodes. In contrast, the configuration where the molecule bridges the electrodes is stable in a wide range of distances. In this last case the bonding state of the molecule does not hybridize with the leads and remains localized within the junction. As a result, this state does not transmit charge so that electronic transport is carried only through the anti-bonding state. This fact leads to conductances of 1 $G_0$ at most, where $G_0=2e^2/h$. We indeed find that G is equal to 0.9 and 0.6 $G_0$ for Pt and Pd contacts respectively.
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Using first principles simulations we perform a detailed study of the structural, electronic and transport properties of monoatomic platinum chains, sandwiched between platinum electrodes. First we demonstrate that the most stable atomic configuration corresponds to a zigzag arrangement that gradually straightens as the chains are stretched. Secondly, we find that the conductance at equilibrium atomic spacing does not oscillate with the number of atoms $n$ in the chain, but instead decreases almost monotonically with $n$. In contrast, the conductances of chains of fixed $n$ oscillate as the end atoms are pulled apart, due to the gradual closing and opening of conductance channels as the chain straightens.
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