New Limit on the Permanent Electric Dipole Moment of $^{129}$Xe using $^{3}$He Comagnetometry and SQUID Detection

TL;DR

This paper introduces a new experimental technique using $^{3}$He comagnetometry and SQUID detection to measure the electric dipole moment of $^{129}$Xe, achieving a fivefold improvement in sensitivity over previous limits.

Contribution

The authors developed a novel measurement method combining spin-exchange optical pumping, comagnetometry, and SQUID detection to set a new, more stringent limit on the $^{129}$Xe electric dipole moment.

Findings

Set an upper limit of $|d_A(^{129} ext{Xe})| < 1.4 imes 10^{-27} e ext{cm}$ at 95% CL.

Achieved a fivefold sensitivity improvement over the 2001 limit.

Demonstrated systematic effects are well-controlled in the new measurement approach.

Abstract

We report results of a new technique to measure the electric dipole moment of $^{129}$Xe with $^3$He comagnetometry. Both species are polarized using spin-exchange optical pumping, transferred to a measurement cell, and transported into a magnetically shielded room, where SQUID magnetometers detect free precession in applied electric and magnetic fields. The result from a one week measurement campaign in 2017 and a 2.5 week campaign in 2018, combined with detailed study of systematic effects, is $d_A(^{129}\mathrm{Xe}) = (1.4 \pm 6.6_\mathrm{stat} \pm 2.0_\mathrm{syst})\times10^{-28}~e\,\mathrm{cm}$. This corresponds to an upper limit of $|d_A(^{129}\mathrm{Xe})| < 1.4 \times 10^{-27} ~e\,\mathrm{cm}~(95\%~\mathrm{CL})$, a factor of five more sensitive than the limit set in 2001.