Acoustic phonon strain induced mixing of the fine structure levels in colloidal CdSe quantum dots observed by a polarization grating technique

Vanessa Margaret Huxter, Gregory D. Scholes

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Acoustic phonon modes in colloidal semiconductor nanocrystals are of significant interest due to their role in dephasing and as the main component of homogeneous line broadening. Despite their importance, these modes have proven elusive and have only recently been experimentally observed. This paper expands on results presented in our earlier paper [V. M. Huxter, A. Lee, S. S. Lo, Nano Lett. 9, 405 (2008)], where a cross polarized heterodyne detected ultrafast transient grating (CPH-3TG) technique was used to observe the acoustic phonon mode. In the present work, we explain the origin of the observed quantum beat in the CPH-3TG signal. Further experiments are presented that show that the observed quantum beat, which arises from a coherent acoustic phonon mode in the nanocrystals, appears in anisotropy-type signals. The action of this mode induces a periodic strain in the nanocrystal that lowers the symmetry of the unit cell, mixing the fine structure states and their transition dipole moments. This mixing is manifested in anisotropy signals as a depolarization, which periodically modifies the rotational averaging factors. Through observation of the acoustic phonon mode using the CPH-3TG optical technique, it is possible to access its microscopic (atomic-level) basis and to use it as a probe to quantify changing macroscopic (whole particle) material parameters.

Original languageEnglish (US)
Article number104506
JournalThe Journal of Chemical Physics
Volume132
Issue number10
DOIs
StatePublished - 2010
Externally publishedYes

Fingerprint

Semiconductor quantum dots
Acoustics
fine structure
quantum dots
gratings
Nanocrystals
Polarization
acoustics
polarization
nanocrystals
Anisotropy
synchronism
Dipole moment
Depolarization
Crystal symmetry
anisotropy
Semiconductor materials
depolarization
dipole moments
probes

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

@article{365bc6d12f844982ba7f83f01a1446fe,
title = "Acoustic phonon strain induced mixing of the fine structure levels in colloidal CdSe quantum dots observed by a polarization grating technique",
abstract = "Acoustic phonon modes in colloidal semiconductor nanocrystals are of significant interest due to their role in dephasing and as the main component of homogeneous line broadening. Despite their importance, these modes have proven elusive and have only recently been experimentally observed. This paper expands on results presented in our earlier paper [V. M. Huxter, A. Lee, S. S. Lo, Nano Lett. 9, 405 (2008)], where a cross polarized heterodyne detected ultrafast transient grating (CPH-3TG) technique was used to observe the acoustic phonon mode. In the present work, we explain the origin of the observed quantum beat in the CPH-3TG signal. Further experiments are presented that show that the observed quantum beat, which arises from a coherent acoustic phonon mode in the nanocrystals, appears in anisotropy-type signals. The action of this mode induces a periodic strain in the nanocrystal that lowers the symmetry of the unit cell, mixing the fine structure states and their transition dipole moments. This mixing is manifested in anisotropy signals as a depolarization, which periodically modifies the rotational averaging factors. Through observation of the acoustic phonon mode using the CPH-3TG optical technique, it is possible to access its microscopic (atomic-level) basis and to use it as a probe to quantify changing macroscopic (whole particle) material parameters.",
author = "Huxter, {Vanessa Margaret} and Scholes, {Gregory D.}",
year = "2010",
doi = "10.1063/1.3350871",
language = "English (US)",
volume = "132",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "10",

}

TY - JOUR

T1 - Acoustic phonon strain induced mixing of the fine structure levels in colloidal CdSe quantum dots observed by a polarization grating technique

AU - Huxter, Vanessa Margaret

AU - Scholes, Gregory D.

PY - 2010

Y1 - 2010

N2 - Acoustic phonon modes in colloidal semiconductor nanocrystals are of significant interest due to their role in dephasing and as the main component of homogeneous line broadening. Despite their importance, these modes have proven elusive and have only recently been experimentally observed. This paper expands on results presented in our earlier paper [V. M. Huxter, A. Lee, S. S. Lo, Nano Lett. 9, 405 (2008)], where a cross polarized heterodyne detected ultrafast transient grating (CPH-3TG) technique was used to observe the acoustic phonon mode. In the present work, we explain the origin of the observed quantum beat in the CPH-3TG signal. Further experiments are presented that show that the observed quantum beat, which arises from a coherent acoustic phonon mode in the nanocrystals, appears in anisotropy-type signals. The action of this mode induces a periodic strain in the nanocrystal that lowers the symmetry of the unit cell, mixing the fine structure states and their transition dipole moments. This mixing is manifested in anisotropy signals as a depolarization, which periodically modifies the rotational averaging factors. Through observation of the acoustic phonon mode using the CPH-3TG optical technique, it is possible to access its microscopic (atomic-level) basis and to use it as a probe to quantify changing macroscopic (whole particle) material parameters.

AB - Acoustic phonon modes in colloidal semiconductor nanocrystals are of significant interest due to their role in dephasing and as the main component of homogeneous line broadening. Despite their importance, these modes have proven elusive and have only recently been experimentally observed. This paper expands on results presented in our earlier paper [V. M. Huxter, A. Lee, S. S. Lo, Nano Lett. 9, 405 (2008)], where a cross polarized heterodyne detected ultrafast transient grating (CPH-3TG) technique was used to observe the acoustic phonon mode. In the present work, we explain the origin of the observed quantum beat in the CPH-3TG signal. Further experiments are presented that show that the observed quantum beat, which arises from a coherent acoustic phonon mode in the nanocrystals, appears in anisotropy-type signals. The action of this mode induces a periodic strain in the nanocrystal that lowers the symmetry of the unit cell, mixing the fine structure states and their transition dipole moments. This mixing is manifested in anisotropy signals as a depolarization, which periodically modifies the rotational averaging factors. Through observation of the acoustic phonon mode using the CPH-3TG optical technique, it is possible to access its microscopic (atomic-level) basis and to use it as a probe to quantify changing macroscopic (whole particle) material parameters.

UR - http://www.scopus.com/inward/record.url?scp=77949703382&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77949703382&partnerID=8YFLogxK

U2 - 10.1063/1.3350871

DO - 10.1063/1.3350871

M3 - Article

VL - 132

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 10

M1 - 104506

ER -