Electronic torsional sound in linear atomic chains: chemical energy transport at 1000 km/s

TL;DR

This paper introduces electronic torsional vibrational modes called torsitons in linear cumulene chains, which propagate at speeds exceeding sound and carry high energy, revealing new insights into electronic energy transport at the nanoscale.

Contribution

It presents the concept of torsitons as electronic vibrational quanta with high group velocity and energy in cumulene chains, a novel form of energy transport in molecular systems.

Findings

Torsitons propagate faster than sound in cumulene chains.

Maximum torsiton energy reaches a few electronvolts.

Minimum torsiton energy is a few hundred wavenumbers, linked to atomic vibration asymmetry.

Abstract

We investigate entirely electronic torsional vibrational modes in linear cumulene chains. The carbon nuclei of a cumulene are positioned along the primary axis so they can participate only in transverse and longitudinal motions. However, the interatomic electronic clouds behave as a torsion spring with remarkable torsional stiffness. The collective dynamics of these clouds can be described in terms of electronic vibrational quanta, which we name torsitons. It is shown that the group velocity of the wavepacket of torsitons is much higher than the typical speed of sound, because of the small mass of participating electrons compared to the atomic mass. For the same reason the maximum energy of the torsitons in cumulenes is as high as a few electronvolts, while the minimum possible energy is evaluated as a few hundred wavenumbers and this minimum is associated with asymmetry of zero point atomic vibrations. Molecular systems for experimental evaluation of the predictions are proposed.