Biomedical Engineering Reference
In-Depth Information
Chapter 11
Stark Effect and the Measurement of Electric
Fields with Quantum Dot Molecules
Eric Stinaff, Kushal Wijesundara, Mauricio Garrido, and Swati Ramanathan
Abstract
Using the physically separated electron and hole of an interdot exciton
in a quantum dot molecule we have studied local electric fields with extremely high
resolution. By monitoring the interdot exciton energy we have measured an electric
field generated through non-resonant excitation in a Schottky device. A maximum
optically generated field of
3.25 kV/cm was observed which corresponds to 5.04%
of the total applied field. The time decay of the field was found to be in the range of
110-140
∼
s while the onset of the field was shorter than our experimental resolution
(7-8
s).
11.1
Introduction
Since the first observations of molecular wavefunction formation between coupled
quantum dots (QDs), these quantum dot molecule (QDM) structures have been the
subject of increasing interest [
1
-
11
]. The potential use of QDMs for spintronics
and quantum information applications has been supported by observations such as
electric field tunable
g
-factors and exciton lifetimes [
12
-
14
], coherent manipulation,
and multiple spin entanglement [
15
]. In this chapter we will focus on the origin
and uses of the Stark effect in QDMs. The situation in QDMs is quite intriguing as
there are not only intradot exciton states, where the electron and hole predominantly
reside within a single QD, but there are also quite prominent interdot exciton states
[
2
,
4
]. Here, since the electron and hole are localized in separate dots, the exciton
displays a dramatic linear dependence on the local electric field. This Stark shift
of the interdot exciton energy can be controlled through sample growth and may
provide a sensitive probe for local electric fields [
16
].
E. Stinaff (
) K. Wijesundara M. Garrido S. Ramanathan
Clippinger Labs 364, Department of Physics and Astronomy, Ohio University,
Athens, OH 45701, USA
