Bistable Spin Currents from Quantum Dots Embedded in a Microcavity.pdf
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Bistable Spin Currents from Quantum Dots Embedded in a Microcavity
Ivana Djuric and Chris P. Search
Department of Physics and Engineering Physics,
Stevens Institute of Technology, Hoboken, NJ 07030
(Dated: February 6, 2008)
We examine the spin current generated by quantum dots embedded in an optical microcavity.
The dots are connected to leads, which allow electrons to tunnel into and out of the dot. The spin
current is generated by spin flip transitions induced by a quantized electromagnetic field inside the
cavity with one of the Zeeman states lying below the Fermi level of the leads and the other above.
In the limit of strong Coulomb blockade, this model is analogous to the Jaynes-Cummings model
in quantum optics. We find that the cavity field amplitude and the spin current exhibit bistability
as a function of the laser amplitude, which is driving the cavity mode. Even in the limit of a single
dot, the spin current and the Q-distribution of the cavity field have a bimodal structure.
PACS numbers: 42.50.Pq,73.63.Kv,78.67.Hc
I. INTRODUCTION
Optical bistability (OB) occurs when a nonlinear di-
electric is placed inside of optical resonator, which pro-
vides a feedback mechanism for the light. The output
intensity from the resonator can, as a result, have two or
more stable values for a given input intensity that is driv-
ing the cavity and can be made to switch between these
two outputs by varying the input intensity beyond the
bistable region1. The interest in OB systems started in
the 1960’s with Szo?ke′s et al theory of absorptive optical
bistability where the bistability is a result of absorption
by the dielectric medium2. OB was first observed ex-
perimentally and explained by Gibbs et al.3 for a cavity
containing a medium with a nonlinear index of refrac-
tion and no absorption or gain (dispersive bistability).
Interest in OB has been stimulated by it
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