Ultra-Low Temperature Magneto-Thermal Microscope Based on NanoSQUID-on-Tip Technique

Nanoscale SQUID-on-tip (nSOT) microscopy has demonstrated exceptional magneto-thermal sensitivity at higher temperatures[1,2]. However, extending its functionality to dilution refrigerator temperatures has been challenging due to the lack of an effective thermal exchange medium[3]. Here, we develop an integrated nSOT microscope housed in a cold-loadable superfluid helium cell, providing efficient thermal coupling between the nSOT sensor and the sample at ultra-low temperatures. The helium gas is managed by a dedicated gas handling system, while an independent insert pre-cools and condenses the superfluid helium into a custom vacuum-tight cell, which is thermally anchored to the mixing chamber. To assess the system’s performance, we utilize a nanoscale wire device to generate local thermal and magnetic gradients, enabling precise quantification of the relative vibrations between the nSOT sensor and the sample. Additionally, by incorporating transport measurement capabilities, our tool extends the potential of nSOT microscopy to investigate quantum states stabilized at ultra-low temperatures, such as anyonic quasiparticles exhibiting non-abelian quantum statistics. Our advancement provides a powerful platform for probing the thermal and magnetic properties of these exotic states of matter.