Sensing with semiconductor quantum dots (Conference Presentation)

International audienceSemiconductor quantum dots (QDs) are solid-state artificial atoms which host spectrally-narrow optical transitions. In this talk, I will review recent results showing that a single QD integrated into a tapered nanowire can find interesting applications to sensing. First, a self-assembled QD integrated at the base of a vertical nanowire constitutes a sensitive probe of the nanowire motion. When the wire oscillates, the QD experiences an oscillating mechanical stress which modulates the spacing between its energy levels. Optical QD spectroscopy then enable to detect the wire motion [1]. Interestingly, the vertical geometry (wire axis parallel to the QD growth axis) optimizes the sensitivity to the oscillating (uniaxial) stress [2]. Furthermore, optimal detection performance are achieved with resonant QD optical spectroscopy: one can then resolve the thermal motion of various mechanical modes, even at liquid helium temperature [3]. Finally, the coupling to a set of vibration modes can be exploited to map the QD position in the wire section with an accuracy as good as one nanometer [4,5]. As a second application to sensing, I will discuss preliminary results showing that nanowire QD can be also used as a scanning probe to map electric field [5]. References: [1] Yeo et al., Nature Nanotech. 9, 106 (2014) [2] P. Stepanov et al., Nano Lett. 16, 3215 (2016) [3] P.-L. De Assis et al., Phys. Rev. Lett. 118, 117401 (2017) [4] M. Munsch et al., Nature Comm. 8, 76 (2017) [5] D. Cadeddu et al., under review at Phys. Rev. Appl