Sensitivity of nuclear clocks to new physics

The recent demonstration of laser excitation of the ≈8 eV isomeric state of ²²⁹Th is a significant step towards a nuclear clock. The low excitation energy likely results from a cancellation between electromagnetic and strong contributions, which new physics can disrupt. In this Letter, we quantify the enhancement of a nuclear clock's sensitivity to new physics using a geometric model and a novel d-wave halo model of the nucleus that reproduces measured differences between ²²⁹Th states. We find likely enhancements of order 104, while a worst case with enhancement « 1 is unlikely.