Towards cooling nanoelectronic devices to microkelvin temperatures : design, construction and test of a novel type of refrigerator

摘要

This work presents an important step towards the realisation of sub-millikelvinudtemperatures in nanoelectronic devices. The ability to reach low millikelvin or evenudmicrokelvin temperatures in nanoelectronic devices would open up the chance touddiscover new physics in various systems.udWe layout a new approach aimed at cooling nanostructures to microkelvin temperatureudbased on the well established technique of adiabatic nuclear demagnetisation:udeach device measurement lead incorporates its own, individual nuclear refrigerator, allowing efficient thermal contact to a microkelvin bath. This schemeudshort-circuits two main bottlenecks of cooling electrons: thermal boundary resistanceudand electron-phonon coupling.udWe have addressed the technical challenges and constructed a parallel network of nuclear refrigerators, yielding a prototype which proved to achieve temperaturesudof � 1mK simultaneously on ten measurement leads upon demagnetisation. Thus, we have accomplished the first step towards ultracold nanoscale samples.udIt was also found that a field and ramp rate dependent heat leak limited the performance and hindered us to reach for lower temperatures.