Demonstration of a scalable all-solid-state refrigerator exploiting diffusion geometries and limiting interfacial conductances at temperatures below 1 kelvin
Abstract
Solid-state refrigerators using Normal-metal/Insulator/Superconductor (NIS) junctions have previously demonstrated excellent electron cooling but limited ability to cool phonons. The energy gap of the superconductor is used as an energy filter to allow higher than average energy electrons to preferentially tunnel from the normal-metal through the insulator into the superconductor where they travel as quasi-particles. Typically, the heat is moved and work is done to deposit hot quasi-particles into a normal-metal quasi-particle trap for rejection to the next refrigeration stage. Realizing that (1) the quasi-particles flow diffusively, driven by a concentration gradient in the electric field-free superconductor, and (2) that the undesirable backwards leaking of heat from the hot-side trap can be reduced by engineering the geometry and materials at the superconductor-to-trap interface, enhanced cooling can be achieved. Fabrication of the refrigerator was accomplished using a tungsten and titanium-tungsten alloy as the cold-side normal-metal, aluminum oxide as the insulator, aluminum as the superconductor, and gold as the trap, with the cold-side NIS portion being attached to the hot-side gold trap by bump bonding. The refrigerator consisted of 1121 junction pairs, each pair being an SINIS unit, all electrically connected in series. Using this we have measured the effective phonon temperature of a 3.9 mm x 3.9 mm x 0.65 mm silicon chip driven down to 70 mK from a bath temperature of 120 mK, and down to 174 mK from a 271 mK rejection temperature (a cooling of -97 mK). This is the first demonstration of the sub 1 K cooling of an entire silicon chip using NIS junctions.
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BibTeX
@misc{young2026demonstration,
title = {{Demonstration of a scalable all-solid-state refrigerator exploiting diffusion geometries and limiting interfacial conductances at temperatures below 1 kelvin}},
author = {Robert M. Young and Zachary Stegen and John X. Przybysz and Edward R. Engbrecht and Aaron A. Hathaway and Justin C. Hackley and Kirby B. Myers and Christian C. Thorpe and Aurelius L. Graninger and Robert Miller and Diego A. Morales and Roberto D. Carcamo and Glen Walters and Jeric P. Sarad and Nicholas F. Pleim and Seth Whitsitt and Joshua T. Shipman and Anil Erol and Melissa G. Loving and Evan Donohue and Corey A. Kegerreis and Benjamin Dalfort and Moe S. Khalil and Christopher Pinion and Randi Jaramillo and John Milinichik and Sandro J. Di Giacomo and Thomas Zodda and Nilesh Tralshawala and Gregory R. Boyd and Jonathan M. Cochran and Katherine A. Maddock and Michael P. De Feo and Aaron A. Pesetski and Marc E. Sherwin},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.17125},
eprint = {2608.17125},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.17125},
}
RIS
TY - UNPB
TI - Demonstration of a scalable all-solid-state refrigerator exploiting diffusion geometries and limiting interfacial conductances at temperatures below 1 kelvin
AU - Robert M. Young
AU - Zachary Stegen
AU - John X. Przybysz
AU - Edward R. Engbrecht
AU - Aaron A. Hathaway
AU - Justin C. Hackley
AU - Kirby B. Myers
AU - Christian C. Thorpe
AU - Aurelius L. Graninger
AU - Robert Miller
AU - Diego A. Morales
AU - Roberto D. Carcamo
AU - Glen Walters
AU - Jeric P. Sarad
AU - Nicholas F. Pleim
AU - Seth Whitsitt
AU - Joshua T. Shipman
AU - Anil Erol
AU - Melissa G. Loving
AU - Evan Donohue
AU - Corey A. Kegerreis
AU - Benjamin Dalfort
AU - Moe S. Khalil
AU - Christopher Pinion
AU - Randi Jaramillo
AU - John Milinichik
AU - Sandro J. Di Giacomo
AU - Thomas Zodda
AU - Nilesh Tralshawala
AU - Gregory R. Boyd
AU - Jonathan M. Cochran
AU - Katherine A. Maddock
AU - Michael P. De Feo
AU - Aaron A. Pesetski
AU - Marc E. Sherwin
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2608.17125
UR - https://arxiv.org/abs/2608.17125
AB - Solid-state refrigerators using Normal-metal/Insulator/Superconductor (NIS) junctions have previously demonstrated excellent electron cooling but limited ability to cool phonons. The energy gap of the superconductor is used as an energy filter to allow higher than average energy electrons to preferentially tunnel from the normal-metal through the insulator into the superconductor where they travel as quasi-particles. Typically, the heat is moved and work is done to deposit hot quasi-particles into a normal-metal quasi-particle trap for rejection to the next refrigeration stage. Realizing that (1) the quasi-particles flow diffusively, driven by a concentration gradient in the electric field-free superconductor, and (2) that the undesirable backwards leaking of heat from the hot-side trap can be reduced by engineering the geometry and materials at the superconductor-to-trap interface, enhanced cooling can be achieved. Fabrication of the refrigerator was accomplished using a tungsten and titanium-tungsten alloy as the cold-side normal-metal, aluminum oxide as the insulator, aluminum as the superconductor, and gold as the trap, with the cold-side NIS portion being attached to the hot-side gold trap by bump bonding. The refrigerator consisted of 1121 junction pairs, each pair being an SINIS unit, all electrically connected in series. Using this we have measured the effective phonon temperature of a 3.9 mm x 3.9 mm x 0.65 mm silicon chip driven down to 70 mK from a bath temperature of 120 mK, and down to 174 mK from a 271 mK rejection temperature (a cooling of -97 mK). This is the first demonstration of the sub 1 K cooling of an entire silicon chip using NIS junctions.
ER -