Change of Decoherence Scenario and Appearance of Localization due to Reservoir Anharmonicity

Although coupling to a super-Ohmic bosonic reservoir leads only to partial dephasing on short time scales, exponential decay of coherence appears in the Markovian limit (for long times) if anharmonicity of the reservoir is taken into account. This effect not only qualitatively changes the decoherence scenario but also leads to localization processes in which superpositions of spatially separated states dephase with a rate that depends on the distance between the localized states. As an example of the latter process, we study the decay of coherence of an electron state delocalized over two semiconductor quantum dots due to anharmonicity of phonon modes.

Figure 1

Left: the dependence of the localization time on temperature for $L=4\mathrm{nm}$ (inset shows the low-temperature sector). Right: the dependence on the distance between the states for $L=4\mathrm{nm}$ (solid lines) and $L=8\mathrm{nm}$ (dashed).