Speaker
Description
While astronomical observations confirm the existence of dark matter, its physical nature remains unknown. For ultralight dark matter (ULDM), its large number density can induce a continuous force on macroscopic targets, allowing detection through precision acceleration measurements. In particular, when the ULDM wavelength matches the target's scale, coherent scattering from all nucleons quadratically enhances the signal.
Here, we analyze data from the MICROSCOPE space mission to constrain the dark matter–nucleon scattering cross section. Designed to test the Weak Equivalence Principle by measuring the differential acceleration of two concentric cylinders with exceptional precision, MICROSCOPE is also uniquely sensitive to a potential dark-matter wind. We demonstrate that the nested-cylinder geometry of MICROSCOPE gives rise to a novel interference effect in ULDM wave scattering, where the scattering amplitudes from the two cylinders interfere and redistribute the induced force. By developing a comprehensive theoretical framework to model this signal, we analyze the MICROSCOPE data to set leading constraints on the dark matter–nucleon coupling for ULDM masses in the range of 10^(-3)–10^(-2) eV, reaching cross sections as small as 10^(-52) cm^2 [1].
On the other hand, ultralight dark matter bosons may act as force carriers, mediating spin-dependent exotic interactions. In a complementary effort, we have experimentally searched for such forces using a precision cantilever sensor and modulated spin sources, establishing the most stringent constraints on such interactions at the micrometer scale [2].
[1] Macroscopic quantum interference in dark matter wave scattering with MICROSCOPE, Cheng-Tao Fu, Pengshun Luo, Rui Luo, Jie Sheng, Chuan-Yang Xing, arXiv:2606.07008.
[2] Improved limits on the spin- and velocity-dependent exotic interaction in the micrometer range, Sumin Li, Wenbo Zhang, Rui Luo, Jinquan Liu, Pengshun Luo, Physical Review Letters 134, 251601 (2025); arXiv:2501.10973.