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 beta is less than 1.9 x 10(7) for n = 1 at 95% confidence level, where n is an input parameter of the self-interaction of the chameleon field phi inversely proportional to phi(n). (C) 2015 The Authors. Published by Elsevier B.V.