What microscopic process produces the excess in cryogenic calorimeters? · revision history

Revision 2

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Title
What microscopic process produces the excess in cryogenic calorimeters?
Plain
Crystals cooled near absolute zero record many more small heat pulses below a few hundred electron volts than expected, and the rate fades over weeks after cooling. The question is what inside the detector releases this energy.
Precise · changed · core
Revision 1: Cryogenic calorimeters (CRESST CaWO4, Al2O3, Si; SuperCDMS-type Si and Ge; NUCLEUS; EDELWEISS) observe a rate $\mathrm{d}R/\mathrm{d}E$ rising steeply below about 200 eV, uncorrelated with particle backgrounds and decaying after cooldown. Candidate sources include stress relaxation at holders, glue and sensor films; dislocation motion from differential thermal contraction; and annealing of radiation-induced lattice defects. An answer is a mechanism that reproduces the energy spectrum, the time dependence, the material dependence and the sensor-geometry dependence, confirmed by a controlled test that turns the excess on or off.
Revision 2: Cryogenic calorimeters (CRESST $\mathrm{CaWO_4}$, $\mathrm{Al_2O_3}$, Si; SuperCDMS-type Si and Ge; NUCLEUS; EDELWEISS) observe a rate $\mathrm{d}R/\mathrm{d}E$ rising steeply below about 200 eV, uncorrelated with particle backgrounds and decaying after cooldown. Candidate sources include stress relaxation at holders, glue and sensor films; dislocation motion from differential thermal contraction; and annealing of radiation-induced lattice defects. An answer is a mechanism that reproduces the energy spectrum, the time dependence, the material dependence and the sensor-geometry dependence, confirmed by a controlled test that turns the excess on or off.
Settled by
A detector in which removing or adding the hypothesized source (e.g., stress in the holder or film, or a defect population) changes the excess rate by a predicted factor.
Kind
phenomenon
Answer type
mechanism
References
(empty)
Literature status
contested
Status note
In 2026 NUCLEUS (Eur. Phys. J. C 86, 831) found slower cooldown lowers the initial rate and the rate decays as a power law independent of particle background; stress-relaxation (Nature Commun. 2024), thermal-contraction (2026 preprint) and defect-annealing (Phys. Rev. Mater. 2025) explanations all remain under discussion.
Posed since
(empty)

Decisions