Phonon-blocked junction calorimeter

Abstract: This study introduces a cold-electron microcalorimeter based on phonon-blocked junctions, integrating on-chip electron cooling and boundary phonon isolation to achieve exceptional energy resolution and rapid thermal response. A general theoretical framework is presented, along with derived approximate analytical expressions for key performance metrics, including cooling efficiency, thermal time constant, and energy resolution. The work examines the influence of device parameters, including non-ideal effects such as subgap tunneling and heat backflow, and offers insights into optimizing detector performance. The findings highlight the potential of phonon-blocked junction microcalorimeters to rival or outperform the state-of-art technologies, such as transition-edge sensors, paving the way for applications requiring precise and fast energy detection.