Thesis Defense: Cryogenic Charge Sensing for Dark Matter Searches: Quantum Sensing and Narrow-Gap Materials

Speaker: Jadyn Anczarski (KIPAC) In Person and zoom

Ph.D. Candidate: Jadyn Anczarski
Research Advisor: Noah Kurinsky

Public Zoom Link: https://stanford.zoom.us/j/92997243346?pwd=y8DQ2QVBlpczHqXxCfhQmj0lg5aJrX.1

Abstract:  Dark matter makes up about 85% of the matter in the universe, yet no direct-detection experiment has observed a confirmed (5σ) signal. With much of the GeV-scale parameter space now explored, sub-MeV dark matter remains largely unprobed because the eV-scale bandgaps of current semiconductor detectors set the lowest detectable dark matter mass. The SPLENDOR Collaboration’s approach to sub-MeV dark matter is to synthesize novel narrow-gap semiconductors with bandgaps of order 10–100 meV. Detecting ionization in these materials requires a new detector platform that allows candidate substrates to be swapped easily, without complex fabrication, while reaching sub-electron charge resolution. This talk presents SPLENDOR’s first charge amplifier, a two-stage design based on low-noise cryogenic transistors (CryoHEMTs), which achieved a charge resolution of about 20 electrons, with a projected resolution of about 3 electrons with amplifier improvements. This talk then presents a second charge amplifier based on superconducting quantum circuits, specifically a cavity-embedded Cooper pair transistor, including its design, initial performance, and projected charge sensitivity. This work pushed established CryoHEMT amplifiers toward their single-electron limit and produced an initial superconducting quantum circuit designed for charge sensing in macroscopic substrates.