Chirality-Selective Excitation of Coherent Phonons in Carbon Nanotubes

TL;DR

This study demonstrates selective excitation of coherent phonons in specific-chirality carbon nanotubes using femtosecond pulses, revealing diameter expansion and oscillating excitonic absorption peaks linked to radial breathing modes.

Contribution

It introduces a method for chirality-selective phonon excitation in carbon nanotubes and links diameter oscillations to excitonic absorption dynamics.

Findings

Selective excitation of radial breathing mode phonons

Diameter expansion occurs immediately after ultrafast excitation

Excitonic absorption peaks oscillate with the phonons

Abstract

Using pre-designed trains of femtosecond optical pulses, we have selectively excited coherent phonons of the radial breathing mode of specific-chirality single-walled carbon nanotubes within an ensemble sample. By analyzing the initial phase of the phonon oscillations, we prove that the tube diameter initially increases in response to ultrafast photoexcitation. Furthermore, from excitation profiles, we demonstrate that an excitonic absorption peak of carbon nanotubes periodically oscillates as a function of time when the tube diameter undergoes radial breathing mode oscillations.