Speaker
Description
Graphene-based Josephson junction detectors are a promising platform for detecting low-energy events, leveraging graphene’s exceptionally low electron heat capacity, intrinsically weak electron–phonon coupling, and the strong temperature dependence of the junction switching current [1]. Recently, we proposed a new strategy for detecting ultra-light dark matter with masses as low as 0.1 keV using graphene-based Josephson junction detectors [2]. In this work, we introduce a detector calibration method that utilizes microwave pulses of varying amplitude for detection efficiency and dark count probability. Using this method, we experimentally quantify the detector performance as a function of deposited energy: the threshold energy is 10.5 meV with a dark count rate of 1670 cps, and at 36.4 meV we achieve a detection efficiency of 95% with a dark count rate of 3×10⁻³ cps. This calibration technique enables the precise determination of the mass range of dark matter that the detector can detect. In addition, the thermal relaxation time of graphene was also quantitatively analyzed with the time-resolved two-pulse experiment. From the time-resolved two-pulse measurement, we extract a thermal relaxation time of 18.5 ns. This provides information on thermal properties of graphene at low-temperature, which is valuable for optimizing detector performance.
[1] E. D. Walsh et al., Phys. Rev. Appl. 8, 024022 (2017); G.-H. Lee, Nature 586, 42 (2020); R. Kokkoniemi, Nature 586, 47 (2020).
[2] D. Kim et al., Phys. Rev. D 112, 015002 (2025).
| Main Contribution topic | Instrumentation for Dark Matter searches |
|---|---|
| Secondary contribution topic | Light Dark Matter |