Coulomb blockade thermometry based nanocalorimetry

Specific heat is a powerful probe offering insights into the entropy and excitation spectrum of the studied material. While it is well established, a key challenge remains the measurement of microcrystals or thin films, especially in the sub-Kelvin, high magnetic field regime. Here, we present a setup combining the high sensitivity of SiNx membrane based calorimetry with the absolute accuracy of Coulomb blockade thermometry to realize a nanocalorimeter for such tasks. The magnetic field independent technique of Coulomb blockade thermometry provides an on-platform thermometer combining a primary thermometry mode for in situ calibration with a fast secondary mode suitable for specific heat measurements. The setup is validated using measurements of a 20 μg sample of Sr₃Ru₂O₇, achieving a resolution on the order of 0.1 nJ K⁻¹ at 500 mK and an absolute accuracy limited by the determination of the sample’s mass. Measurements of CeRh₂As₂ further highlight the benefits of measuring microcrystals with such a device.