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Title: Excitonic Exchange Splitting and Radiative Lifetime in PbSe Quantum Dots

Abstract

An exciton evolving from an m-fold degenerate hole level and an n-fold degenerate electron level has a nominal m x n degeneracy, which is often removed by electron-hole interactions. In PbSe quantum dots, the degeneracy of the lowest-energy exciton is m x n = 64 because both the valence-band maximum and the conduction-band minimum originate from the 4-fold degenerate (8-fold including spin) L valleys in the Brillouin zone of bulk PbSe. Using a many-particle configuration-interaction approach based on atomistic single-particle wave functions, we have computed the fine structure of the lowest-energy excitonic manifold of two nearly spherical PbSe quantum dots of radius R = 15.3 and 30.6 {angstrom}. We identify two main energy splittings, both of which are accessible to experimental probe: (i) The intervalley splitting is the energy difference between the two near-edge peaks of the absorption spectrum. We find {delta} = 80 meV for R = 15.3 {angstrom} and {delta} = 18 meV for R = 30.6 {angstrom}. (ii) The exchange splitting {Delta}{sub x} is the energy difference between the lowest-energy optically dark exciton state and the first optically bright exciton state. We find that {Delta}{sub x} ranges between 17 meV for R = 15.3 {angstrom}, and 2more » meV for R = 30.6 {angstrom}. We also find that the room-temperature radiative lifetime is {tau}{sub R} {approx} 100 ns, considerably longer than the {approx}10 ns radiative lifetime of CdSe dots, in quantitative agreement with experiment.« less

Authors:
; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
939525
DOE Contract Number:  
AC36-99-GO10337
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nano Letters; Journal Volume: 7; Journal Issue: 7, 2007
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 77 NANOSCIENCE AND NANOTECHNOLOGY; ABSORPTION; BRILLOUIN ZONES; CONFIGURATION INTERACTION; ELECTRONS; EXCITONS; FINE STRUCTURE; LIFETIME; QUANTUM DOTS; SPIN; VALLEYS; WAVE FUNCTIONS; Basic Sciences; Solid State Theory

Citation Formats

An, J. M., Franceschetti, A., and Zunger, A.. Excitonic Exchange Splitting and Radiative Lifetime in PbSe Quantum Dots. United States: N. p., 2007. Web. doi:10.1021/nl071219f.
An, J. M., Franceschetti, A., & Zunger, A.. Excitonic Exchange Splitting and Radiative Lifetime in PbSe Quantum Dots. United States. doi:10.1021/nl071219f.
An, J. M., Franceschetti, A., and Zunger, A.. Mon . "Excitonic Exchange Splitting and Radiative Lifetime in PbSe Quantum Dots". United States. doi:10.1021/nl071219f.
@article{osti_939525,
title = {Excitonic Exchange Splitting and Radiative Lifetime in PbSe Quantum Dots},
author = {An, J. M. and Franceschetti, A. and Zunger, A.},
abstractNote = {An exciton evolving from an m-fold degenerate hole level and an n-fold degenerate electron level has a nominal m x n degeneracy, which is often removed by electron-hole interactions. In PbSe quantum dots, the degeneracy of the lowest-energy exciton is m x n = 64 because both the valence-band maximum and the conduction-band minimum originate from the 4-fold degenerate (8-fold including spin) L valleys in the Brillouin zone of bulk PbSe. Using a many-particle configuration-interaction approach based on atomistic single-particle wave functions, we have computed the fine structure of the lowest-energy excitonic manifold of two nearly spherical PbSe quantum dots of radius R = 15.3 and 30.6 {angstrom}. We identify two main energy splittings, both of which are accessible to experimental probe: (i) The intervalley splitting is the energy difference between the two near-edge peaks of the absorption spectrum. We find {delta} = 80 meV for R = 15.3 {angstrom} and {delta} = 18 meV for R = 30.6 {angstrom}. (ii) The exchange splitting {Delta}{sub x} is the energy difference between the lowest-energy optically dark exciton state and the first optically bright exciton state. We find that {Delta}{sub x} ranges between 17 meV for R = 15.3 {angstrom}, and 2 meV for R = 30.6 {angstrom}. We also find that the room-temperature radiative lifetime is {tau}{sub R} {approx} 100 ns, considerably longer than the {approx}10 ns radiative lifetime of CdSe dots, in quantitative agreement with experiment.},
doi = {10.1021/nl071219f},
journal = {Nano Letters},
number = 7, 2007,
volume = 7,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}