Performance of a SuperCDMS HVeV Detector with Sub-eV Energy Resolution and Single Charge-sensitivity

TL;DR

This paper reports on a new Si HVeV detector with sub-eV energy resolution and single-charge sensitivity, enabling precise single-photon measurements and establishing it as the most efficient athermal phonon detector to date.

Contribution

The paper introduces a new generation of athermal-phonon Si HVeV detectors with record energy resolution and efficiency, and provides detailed characterization and modeling of their performance.

Findings

Achieved 612 meV baseline resolution in detectors.

Measured consistent energy loss of 0.81 eV per charge excitation.

Established athermal phonon detector efficiency limit at 45%.

Abstract

We present a detailed characterization of a new generation of athermal-phonon single-charge sensitive Si HVeV detectors, the best of which achieved 612 meV $\pm$ 4 meV baseline resolution. Our sub-eV energy resolution enables precise measurements of single-photon events and reveal consistent energy losses of 0.81 eV $\pm$ 0.03 eV per charge excitation across two facilities. We demonstrate that the noise for these detectors is well described using a standard Transition Edge Sensor noise model. We also place upper bounds on the nominal phonon collection efficiency of 45\%, establishing these detectors as the most efficient athermal phonon detectors to date, limited only by intrinsic limitations of quasiparticle generation.