Search for new physics using a 129Xe-131Xe-Rb comagnetometer

In a compact 129Xe-131Xe-Rb comagnetometer, polarized Rb atoms are used both to hyperpolarize Xe atoms and to serve as an in-situ magnetometer to sense the nuclear spin signals of Xe atoms. The two Xe isotopes are chosen for their long nuclear spin coherence times, and for their nearly equal collisional shifts in the Rb vapor. To suppress the effect due to the nuclear quadrupole moment of 131Xe, we amplify and resolve the quadrupole splittings by deliberately employing an elongated cell geometry. A modulated Rb polarization scheme is used to suppress systematic effects by two orders of magnitude. We have used this comagnetometer to search for monopole-dipole interactions at the sub-millimeter range and spin-dependent gravitational interactions at the Earth range. In both searches, we measure the ratio of nuclear spin-precession frequencies between 129Xe and 131Xe, and search for a correlated change of this ratio with either the movement of an external mass or the sensor orientation in the Earth gravitational field. The null results of both experiments set new upper limits on the coupling strength of aforementioned exotic interactions.