We develop a new comagnetometer using 21Ne atoms with nuclear spin I=3/2 and Rb atoms polarized by spin-exchange with K atoms to search for tensor interactions that violate local Lorentz invariance. We frequently reverse orientation of the experiment and search for signals at the first and second harmonics of the sidereal frequency. We constrain 4 of the 5 spatial Lorentz-violating coefficients cjkn that parameterize anisotropy of the maximum attainable velocity of a neutron at a level of 10−29, improving previous limits by 2 to 4 orders of magnitude and placing the most stringent constrain on deviations from local Lorentz invariance.
@article{arxiv.1106.0738,
title = {A new test of local Lorentz invariance using $^{21}$Ne-Rb-K comagnetometer},
author = {M. Smiciklas and J. M. Brown and L. W. Cheuk and M. V. Romalis},
journal= {arXiv preprint arXiv:1106.0738},
year = {2015}
}