Spin-Rotation Coupling observed in Neutron Interferometry

February 14, 2020 11:44 am Published by Stephan Sponar

In our latest neutron interferometric ¹ experiment the effect of spin–rotation coupling, also referred to as Sagnac–Mashhoon phase was measured with neutrons. The coupling of spin with the angular velocity of a rotating magnetic field is an extension of the well-known Sagnac effect, including the intrinsic spin of a quantum mechanical particle when replacing the orbital angular momentum, denoted as , by the total angular momentum (see here for details of the underlying theory). The principle of the experiment (see here for experimental details), which is schematically illustrated below, is the following: in one path of the interferometer the neutron’s spin is manipulated by a rotating magnetic field to undergo a cyclic path. As the orientations before and after the manipulation are the same, only a phase difference between the sunbeams is induced. This phase difference results in a shift of the observed interference fringes which turns out to depend solely on the frequency of the rotation of the magnetic field, as can be seen in the final results below on the right side. The experimental results agree well with the solutions acquired by solving the Pauli–Schrödinger equation.