Microkelvin electronics on a pulse-tube cryostat with a gate Coulomb blockade thermometer

TL;DR

This paper introduces a pulse-tube compatible microkelvin sample holder with on-board cooling and a novel gate Coulomb blockade thermometer, achieving electronic temperatures as low as 224 microkelvin and enabling advanced quantum experiments.

Contribution

The authors develop a new microkelvin cooling setup compatible with pulse-tube cryostats and introduce a novel gate Coulomb blockade thermometer for ultra-low temperature measurement.

Findings

Achieved electronic temperatures of 224±7 μK.

Maintained temperatures below 300 μK for 27 hours.

Demonstrated potential for cooling below 50 μK.

Abstract

Access to lower temperatures has consistently enabled scientific breakthroughs. Pushing the limits of \emph{on-chip} temperatures deep into the microkelvin regime would open the door to unprecedented quantum coherence, novel quantum states of matter, and also the discovery of unexpected phenomena. Adiabatic demagnetization is the workhorse of microkelvin cooling, requiring a dilution refrigerator precooling stage. Pulse-tube dilution refrigerators have grown enormously in popularity due to their vast experimental space and independence of helium, but their unavoidable vibrations are making microkelvin cooling very difficult. On-chip thermometry in this unexplored territory is also not a trivial task due to extreme sensitivity to noise. Here, we present a pulse-tube compatible microkelvin sample holder with on-board cooling and microwave filtering and introduce a new type of temperature sensor, the gate Coulomb blockade thermometer (gCBT), working deep into the microkelvin regime. Using on- and off-chip cooling, we demonstrate electronic temperatures as low as 224$\pm$7$\mu$K, remaining below 300$\mu$K for 27 hours, thus providing sufficient time for measurements. Finally, we give an outlook for cooling below 50$\mu$K for a new generation of microkelvin transport experiments.