Inelastic scattering in nanostructures

The rapid evolution in electronics towards smaller and faster devices will eventually reach the fundamental level set by the atomistic structure of matter. Atomic-size conductors like the atomic gold wire shown below, take this development to the extreme of miniaturization. Understanding their properties is an important problem in the emerging fields of nanoelectronics and molecular electronics. One relevant aspect is the study of the effects caused by atomic vibrations, since inelastic scattering of traversing electrons and energy dissipation play essential roles for device characteristics, working conditions, and stability.

We model the inelastic transport through small devices connected to metallic contacts using the self-consistent Born approximation (SCBA) combined with non-equilibrium Green’s functions (NEGF). The electronic structure of the system is described with density functional theory which also allows us to calculate phonon energies and the electron-phonon interaction strength.

The conductance of the atomic gold chain is shown below.  

At a bias voltage corresponding to the phonon energy, the incoming electrons can emit phonons into the gold wire. This scattering gives rise to the decrease in conductance. The slope of the conductance at higher biases is caused by the heating, i.e., increase of the number of phonons.

Publications:

• Inelastic Scattering and Local Heating in Atomic Gold Wires, PRL 93, 256601 (2004)

• Modeling inelastic phonon scattering in atomic- and molecular-wire junctions, PRB 72, 201101R (2005)

• Inelastic transport through molecules: Comparing first principles calculations to experiments, Nano Lett. 6, 258 (2006) ( pdf)

Interested to learn more? Contact Mads Brandbyge.