Voltage-controlled motional narrowing in a semiconductor quantum dot

International audienceWe demonstrate the control with a dc-voltage of the environment-induced decoherence in a semiconductor quantum dot embedded in a gated ¯eld-e®ect device. The electrical control of the spectral di®usion dynamics governing the quantum dot decoherence induces various e®ects, and in particular a narrowing of the quantum dot emission spectrum on increasing the electric ¯eld applied to the structure. We develop a model in the framework of the pre-Gaussian noise theory that provides a quantitative interpretation of our data as a function of gate voltage. The standard phenomenology of motional narrowing described in nuclear magnetic resonance is successfully reached by hastening the carrier escape from the traps around the quantum dot through tunnelling under reverse bias voltage. Our study paves the way to a protection of zero-dimensional electronic states from outside coupling through a voltage-controlled motional narrowing e®ect