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Phonon Bottleneck Effect in Organic Molecules

Published online by Cambridge University Press:  31 January 2011

S. Bandyopadhyay  and
Bhargava Kanchibotla
S. Bandyopadhyay
Affiliation:
sbandy@mail2.vcu.edu, Virginia Commonwealth University, Electrical and Computer Engineering, 601 W. Main Street, Richmond, Virginia, 23284, United States, 804-827-6275, 804-827-0006
Bhargava Kanchibotla
Affiliation:
kanchibotlbv@vcu.edu, Virginia Commonwealth University, Electrical and Computer Engineering, Richmond, Virginia, United States
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Abstract

We have measured the ensemble averaged transverse spin relaxation time T2* (associated with g = 4 resonance) in bulk powders of the organic molecule Alq3, and in samples containing 1-2 molecules confined in nanocavities of dimension ˜ 2 nm. Both T2* times are strongly temperature dependent indicating that they are determined by phonon-mediated spin relaxation. Interestingly, the T2* time in nanocavities is ˜2.5 times longer than in bulk powder over a wide temperature range. The longer T2* in the nanocavity is evidence of weakened electron-phonon interaction. We believe that electron-phonon interaction is suppressed because the cavity confines phonons and discretizes the phonon modes and phonon energies. As a result, the chances of a phonon induced (inelastic) spin relaxation event are reduced owing to the need to conserve energy in the relaxation process. This is a novel “phonon bottleneck effect” that to our knowledge has not been previously reported.

Keywords

electron spin resonanceelectron-phonon interactionsorganic
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1172: Symposium T – Nanoscale Heat Transport–From Fundamentals to Devices , 2009 , 1172-T02-04
Copyright
Copyright © Materials Research Society 2009

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