Speaker
Description
Searches for spin-dependent interactions mediated by light vector bosons provide a powerful probe of physics beyond the Standard Model. We propose magnetic resonance force microscopy (MRFM) as a new platform for searching for exotic electron-electron interactions mediated by a Z' boson. The proposed system consists of a ferromagnetic mechanical resonator acting as the sensor and a polarized spin ensemble serving as the source, coupled through the magnetic resonance force associated with the longitudinal spin polarization. By investigating the coupled spin-mechanical dynamics, we show that the direct resonant interaction between the sensor and the spin source produces characteristic signatures of the exotic interactions. Compared with existing solid-state spin-based searches, the proposed MRFM scheme employs a macroscopic ferromagnetic tip containing more than 10^9 polarized electron spins while maintaining micrometer-scale tip-sample separations. Furthermore, because MRFM probes the longitudinal spin polarization, the signal accumulation is governed by the synchronization time \tau_m rather than the transverse coherence time T_2, enabling substantially longer interrogation times than pulsed NV magnetometry. Based on experimentally demonstrated MRFM parameters, we project that the proposed scheme can improve the current limits on the axial-vector coupling g_A^eg_A^e by approximately two orders of magnitude over the relevant interaction range, providing a promising new avenue for searching for spin-dependent interactions beyond the Standard Model.