Cross-polarized optical absorption of single-walled nanotubes probed by polarized photoluminescence excitation spectroscopy

TL;DR

This study uses polarized photoluminescence excitation spectroscopy to analyze cross-polarized absorption in single-walled carbon nanotubes, revealing distinct perpendicular excitation peaks and differences in exciton binding energies.

Contribution

It introduces a method to decompose PLE spectra into parallel and perpendicular components, providing new insights into excitonic properties of SWNTs.

Findings

Perpendicular excitation peaks observed in several (n,m) SWNTs.

Perpendicular excitations are blue-shifted relative to single-particle predictions.

Smaller exciton binding energy for perpendicular excitations compared to parallel ones.

Abstract

Cross-polarized absorption peaks of isolated single-walled carbon nanotubes were observed by a polarized photoluminescence excitation (PLE) spectroscopy. Using a simple theory for PL anisotropy, the observed PLE spectra are decomposed into 'pure' components of the photoexcitation for incident light polarized parallel and perpendicular to the SWNT axis. For several (n, m) SWNTs, distinct peaks corresponding to perpendicular excitation were observed. The measured transition energies for perpendicular excitations were blue-shifted compared to the qualitative values predicted within a single-particle theory. The results indicate a smaller exciton binding energy for perpendicular excitations than for parallel excitations.