Probing the Temperature\nof Single Quantum Dots Confined\nin a Nanoparticle Ion Trap by Fluorescence Thermometry

A charged particle trapped in a temperature-controlled\nnanoparticle\nion trap is subjected to various heating and cooling processes, but\nprobing the particle temperature remains difficult. Here, we demonstrate\na method to determine the temperature of a single trapped fluorescent\nCdSe/CdS quantum dot (QD) by measuring its temperature-dependent fluorescence\nspectrum after laser excitation at 532 nm. The QD’s mean fluorescence\nwavelength then yields the QD temperature using the empirical Varshni\nrelation. We observe a linear correlation between the temperatures\nof the QD and ion trap with a slope of one and an offset of 113 K.\nThese experimental results are in satisfactory agreement with a simple\npower balance model and provide detailed insight into the relevance\nof various heating and cooling processes acting on the trapped particles,\nwith photoabsorption, fluorescence, and collisional cooling being\nthe most significant ones.