[2601.16307]
Kyle Kennard, Aditi Pradeep, Mason Buchanan, Hope Fu, Aviv Simchony, Qihua Wang, Emanuele Michielin, Taylor Aralis, Elspeth Cudmore, Priscilla Cushman, Miriam Diamond, Enectali Figueroa-Feliciano, Caleb Fink, Simon Harms, Bruce A. Hines, Ziqing Hong, Martin E. Huber, Andrew Kubik, Noah Kurinsky, Rupak Mahapatra, Valentina Novati, Lekhraj Pandey, Pratyush K. Patel, Weigeng Peng, Mark Platt, Ry Pressman-Cyna, Wolfgang Rau, Runze Ren, Tyler Reynolds, James Ryan, Tarek Saab, David Sadek, Benjamin Schmidt, Zoë Smith, Sidney Stevens, Kelly Stifter, Matthew Stukel, Julius Viol, Yongqi Wang, Matthew James Wilson, Betty Young, Stefan Zatschler, Hazal Zenger, Ariel Zuñiga-Reyes
We present a detailed characterization of a new generation of athermal-phonon single-charge sensitive Si HVeV detectors, the best of which achieved 589~meV~$\pm$~5~meV baseline resolution. Our sub-eV energy resolution enables precise measurements of single-photon events and reveal consistent energy losses of 0.92~eV~$\pm$~0.02~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 measure a nominal phonon collection efficiency of 45\%~$\pm$~3\%~(stat.)~$\pm$~6\%~(syst.) in the best performing device, establishing these detectors as the most efficient athermal phonon detectors to date, limited only by intrinsic limitations of quasiparticle generation.