Electrical Transport Measured in Atomic Carbon Chains
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Abstract
The
first electrical-transport measurements of monatomic carbon
chains are reported in this study. The chains were obtained by unraveling
carbon atoms from graphene ribbons while an electrical current flowed
through the ribbon and, successively, through the chain. The formation
of the chains was accompanied by a characteristic drop in the electrical
conductivity. The conductivity of the chains was much lower than previously
predicted for ideal chains. First-principles calculations using both
density functional and many-body perturbation theory show that strain
in the chains has an increasing effect on the conductivity as the
length of the chains increases. Indeed, carbon chains are always under
varying nonzero strain that transforms their atomic structure from
the <i>cumulene</i> to the <i>polyyne</i> configuration,
thus inducing a tunable band gap. The modified electronic structure
and the characteristics of the contact to the graphitic periphery
explain the low conductivity of the locally constrained carbon chain