Cooling Electrons

A major challenge in the study of low dimensional electron systems created in semiconductor nanostructures has been to “break the 1 mK barrier”. In our laboratory two-dimensional electrons in semiconductor heterostructures have been cooled to  1 mK in an 3He immersion cell, employing a cooling-through-the-leads strategy.

This required [1]:

• the identification and elimination of important sources of heat input
• the development of techniques to both cool and measure diverse electron systems to below 1mK, with ultra-sensitive SQUID magnetometers playing a key role in low dissipation measurement

Together with the increased accessibility of low temperatures through cryogen-free technology, the door is opened to technological applications of relatively fragile exotic ordered states appearing as a result of electron correlations in a range of quantum materials and mesoscopic devices. In this regime competition between interactions allows systems to be relatively easily fine-tuned by external control parameters, such as magnetic field, strain and structured geometry.

Future work will centre on the study of gate-tuned nanoelectronic devices, cooled into this ultralow temperature regime, in which new correlated, spin ordered states are predicted. Cooling low dimensional electron systems in high magnetic fields will be possible on ND3, enabling the study of the exotic Fractional Quantum Hall Effect states.