Low-Temperature Anomaly in Dielectric Behavior: Excited Dipole States and Neutrality Induction in Germanium Detectors for MeV-Scale Dark Matter Detection*

This study delves into an intriguing anomaly in the dielectric behavior of semiconductors at extremely low temperatures, specifically focusing on germanium detectors operated at helium temperatures. Below 11 K, the relative capacitance experiences a rapid decline, stabilizing around 6.5 K, reminiscent of the fully depleted state observed at 77.8 K under ambient conditions. Notably, this neutralization process occurs independently of bias voltage, indicating an intrinsic phenomenon. Consistent measurements affirm this trend, highlighting the induction of neutrality below 6.5 K, with excited dipole states playing a pivotal role in neutralizing the semiconductor's intrinsic charge. This unconventional observation challenges established knowledge and provides fresh insights into semiconductor physics at very low temperatures. The study not only advances theoretical understanding but also introduces a novel concept of detecting MeV-scale dark matter with germanium detectors at helium temperatures, leveraging the low binding energy of these dipole states. A comprehensive analysis sheds light on the underlying mechanisms driving this unique dielectric behavior and subsequent neutrality induction. Beyond its theoretical implications, this research opens innovative avenues for the design and optimization of low-temperature semiconductor devices.