Neutron interferometry constrains dark energy chameleon fields

We present phase shift measurements for neutron matter waves in vacuum and in low pressure Helium using a method originally developed for neutron scattering length measurements in neutron interferometry. We search for phase shifts associated with a coupling to scalar fields. We set stringent limits for a scalar chameleon field, a prominent quintessence dark energy candidate. We find that the coupling constant β   is less than 1.9×1071.9×107 for n=1n=1 at 95% confidence level, where n is an input parameter of the self-interaction of the chameleon field φ   inversely proportional to φnφn.