Temperature sensitivity of a Thorium-229 solid-state nuclear clock

2024/09/17 by Jacob S. Higgins, Higgins, Jacob S., Tian Ooi +13 · 9 citations
Engineering · Physics and Astronomy · #Advanced Frequency and Time Standards #Atomic Physics (physics.atom-ph) #Atomic and Subatomic Physics Research #FOS: Physical sciences #Non-Invasive Vital Sign Monitoring

paper · pdf · doi:10.48550/arxiv.2409.11590

openalex publication_date 2024/09/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/03

Abstract

Quantum state-resolved spectroscopy of the low energy thorium-229 nuclear transition was recently achieved. The five allowed transitions within the electric quadrupole structure were measured to the kilohertz level in a calcium fluoride host crystal, opening many new areas of research using nuclear clocks. Central to the performance of solid-state clock operation is an understanding of systematic shifts such as the temperature dependence of the clock transitions. In this work, we measure the four strongest transitions of thorium-229 in the same crystal at three temperature values: 150 K, 229 K, and 293 K. We find shifts of the unsplit frequency and the electric quadrupole splittings, corresponding to decreases in the electron density, electric field gradient, and field gradient asymmetry at the nucleus as temperature increases. The m = ± 5/2 → ± 3/2 line shifts only 62(6) kHz over the temperature range, i.e., approximately 0.4 kHz/K, representing a promising candidate for a future solid-state optical clock. Achieving 10^-18 precision requires crystal temperature stability of 5μK.

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• A nuclear clock based on ²²⁹Th
• A thorium-229 optical nuclear clock with feedback loop
• A method to detect the VUV photons from cooled 229Th:CaF2 crystals

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