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Modern Physics Letters B

DECOHERENCE STUDY OF ELECTRON SPIN STATES IN QUANTUM DOTS USING A SIMPLISTIC MODEL

Agile Mathew, Malay Kumar Nandy

Published Jun 6, 2013• 2 citations
Publisher

Abstract

Using a simple model of central spin interacting with a spin bath, we study the decoherence of single electron spin states in quantum dots within one-, two- and three-dimensional nanostructure geometries. We consider a one-component hyperfine interaction term and express its strength as a smooth function of position vector. Decoherence measures are evaluated and plotted for various initial states, and we notice a decrease in decoherence time with the reduction of spin-bath dimension.

DOI
10.1142/s0217984913501194

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The dynamics of a spin-1∕21∕21∕2 particle coupled to a nuclear spin bath through an isotropic Heisenberg interaction is studied as a model for the spin decoherence in quantum dots. The time-dependent polarization of the central spin is calculated as a function of the bath-spin distribution and the polarizations of the initial bath state. For short times, the polarization of the central spin shows a Gaussian decay, and at later times it is revived displaying nonmonotonic time dependence. The decoherence time scale depends on moments of the bath-spin distribuition, and also on the polarization strengths in various bath-spin channels. The bath polarizations have a tendency to increase the decoherence time scale. The effective dynamics of the central spin polarization is shown to be described by a master equation with non-Markovian features.
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The dynamics and decoherence of an electronic spin-1/2 qubit coupled to a bath of nuclear spins via hyperfine interactions in a quantum dot is studied. We show how exact results from the integrable solution can be used to understand the dynamic behavior of the qubit. It is possible to predict the main frequency contributions and their broadening for relatively general initial states analytically, leading to an estimate of the corresponding decay times, which are related to T1{T}_{1}T1​ of the electron. Furthermore, for a small bath polarization, a distinct low-frequency time scale is observed.