Quantum Thermometry with Single Molecules in Nanoprobes

An understanding of heat transport is relevant to developing efficient strategies for thermal management in areas of study such as microelectronics, as well as for fundamental science purposes. However, the measurement of temperatures in nanostructured environments and in cryogenic conditions remains a challenging task, requiring both high sensitivity and noninvasive approaches. Here, we present a portable nanothermometer based on a molecular two-level quantum system that operates in the (3-20)-K temperature range, with temperatures and spatial resolutions on the order of millikelvins and micrometers, respectively. We validate the performance of this molecular thermometer by estimating the thermal conductivity of a nanopatterned silicon membrane, where we find a quadratic temperature dependence. In addition, we demonstrate two-dimensional temperature mapping via the simultaneous spectroscopy of multiple probes deposited onto such a suspended membrane. Overall, these results demonstrate the unique potential of the proposed molecular thermometer to explore thermal properties with submicron accuracy and unveil related phenomena manifested at cryogenic temperatures.