Limit on Lorentz-Invariance- and CPT-Violating Neutron Spin Interactions Using a $^3$He-$^{129}$Xe Comagnetometer

TL;DR

This study sets new upper limits on Lorentz-invariance and CPT violation in neutron spin interactions by measuring nuclear spin precession in a $^3$He-$^{129}$Xe comagnetometer, also exploring $^{129}$Xe EDM.

Contribution

It introduces a novel experimental method using a comagnetometer to constrain background fields violating Lorentz invariance and CPT, improving previous limits.

Findings

Upper limit on background field component: < 8.4 x 10^{-34} GeV

Detected no sidereal modulation in spin precession frequencies

Modified technique to search for $^{129}$Xe electric dipole moment

Abstract

We performed a search for a Lorentz-invariance- and CPT-violating coupling of the $^3$He and $^{129}$Xe nuclear spins to posited background fields. Our experimental approach is to measure the free precession of nuclear spin polarized $^3$He and $^{129}$Xe atoms using SQUID detectors. As the laboratory reference frame rotates with respect to distant stars, we look for a sidereal modulation of the Larmor frequencies of the co-located spin samples. As a result we obtain an upper limit on the equatorial component of the background field $\tilde{b}^n_{\bot}< 8.4 \cdot 10^{-34}$ GeV (68\% C.L.). Furthermore, this technique was modified to search for an electric dipole moment (EDM) of $^{129}$Xe.