Title: Renormalization of optical transition strengths in semiconductor nanoparticles due to band mixing

Abstract

We report that unique optical properties of semiconductor nanoparticles (SN) make them very promising in the multitude of applications including lasing, light emission and photovoltaics. In many of these applications it is imperative to understand the physics of interaction of electrons in a SN with external electromagnetic fields on the quantitative level. In particular, the strength of electron–photon coupling determines such important SN parameters as the radiative lifetime and absorption cross section. This strength is often assumed to be fully encoded by the so called Kane momentum matrix element. This parameter, however, pertains to a bulk semiconductor material and, as such, is not sensitive to the quantum confinement effects in SNs. In this work we demonstrate that the quantum confinement, via the so called band mixing, can result in a significant suppression of the strength of electron interaction with electromagnetic field. Within the envelope function formalism we show how this suppression can be described by introducing an effective energy-dependent Kane momentum. Then, the effect of band mixing on the efficiencies of various photoinduced processes can be fully captured by the conventional formulae (e.g., spontaneous emission rate), once the conventional Kane momentum is substituted with the renormalized energy-dependent Kane momentum introducedmore » in here. Lastly, as an example, we evaluate the energy-dependent Kane momentum for spherical PbSe and PbS SNs (i.e., quantum dots) and show that neglecting band mixing in these systems can result in the overestimation of absorption cross sections and emission rates by a factor of ~2.« less

Authors:

Velizhanin, Kirill A. ^[1]

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+ Show Author Affiliations

1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division

Publication Date:

Wed May 25 00:00:00 EDT 2016

Research Org.:

Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Energy Frontier Research Centers (EFRC) (United States). Center for Advanced Solar Photophysics (CASP)

Sponsoring Org.:

USDOE Office of Science (SC). Basic Energy Sciences (BES) (SC-22); USDOE

OSTI Identifier:

1304730

Alternate Identifier(s):

OSTI ID: 1396783

Report Number(s):

LA-UR-16-23593
Journal ID: ISSN 0301-0104

Grant/Contract Number:  

AC52-06NA25396

Resource Type:

Accepted Manuscript

Journal Name:

Chemical Physics

Additional Journal Information:

Journal Name: Chemical Physics; Journal ID: ISSN 0301-0104

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Material Science; semiconductor, optical transitions, gauge invariance