Spontaneous damage annealing reactions as a possible source of low energy excess in semiconductor detectors

Abstract

In semiconductor detectors designed for capturing dark matter particles or neutrinos, when the detection threshold is constantly improved to increasingly low energies, an "excess" signal of apparent energy release events below a few hundred eV is observed in several different kinds of detectors. This becomes a big obstacle to the observation of actual dark matter signals, hindering the detectors' sensitivity for rare events in this energy range. Using atomistic simulations with a classical thermostat and a quantum thermal bath, we show that this kind of signal is consistent with energy release from long-term annealing events of complex defects that can be formed by any kind of nuclear recoil radiation events. Such energy releases are shown to have a very similar exponential dependence on energy release magnitudes as that observed in experiments. By detailed analysis of the annealing events, we show that crossing very low energy barriers can trigger larger energy releases in an avalanche-like effect. This explains why large energy release events can occur even down to cryogenic temperatures, where the significant migration of point defects in silicon is hardly ever possible.

22 pages. 18 figures

References in corpus (12)

• Searching for low-mass dark matter particles with a massive Ge bolometer operated above-ground
• Results on MeV-scale dark matter from a gram-scale cryogenic calorimeter operated above ground
• EXCESS workshop: Descriptions of rising low-energy spectra
• Portable implementation of a quantum thermal bath for molecular dynamics simulations
• Zero-Point Energy Leakage in Quantum Thermal Bath Molecular Dynamics Simulations
• A Stress Induced Source of Phonon Bursts and Quasiparticle Poisoning
• Latest observations on the low energy excess in CRESST-III
• Velocity Dependent Dark Matter Interactions in Single-Electron Resolution Semiconductor Detectors with Directional Sensitivity
• Energy loss in low energy nuclear recoils in dark matter detector materials
• Measurement of the bulk radioactive contamination of detector-grade silicon with DAMIC at SNOLAB
• Repulsive interatomic potentials calculated at three levels of theory
• Aluminum Relaxation as the Source of Excess Low Energy Events in Low Threshold Calorimeters

Cited by in corpus (1)

• Spontaneous generation of athermal phonon bursts within bulk silicon causing excess noise, low energy background events and quasiparticle poisoning in superconducting sensors