Abstract
Long wavelength optical absorption in indirect band gap semiconductors usually relies on phonons to fulfill momentum conservation. However, the near-field of a localized surface plasmon on a metal nanoparticle is itself rapidly varying in space and, thereby, contains Fourier components corresponding to large momenta. We analyze to what extent such a near-field can give rise to light absorption for energies below the direct band gap without phonon assistance. The analysis is based on rigorous quantum response functions for transverse and longitudinal wave vectors. We demonstrate that under realistic conditions such nonlocal absorption is small and provide quantitative spectra for metal nanospheres embedded in crystalline silicon (c-Si) which is of potential importance for plasmonic photovoltaics. Our results contradict previous reports and we determine the source of the discrepancy.
- Received 3 August 2011
- Publisher error corrected 31 October 2011
DOI:https://doi.org/10.1103/PhysRevB.84.165447
©2011 American Physical Society
Corrections
31 October 2011