Searching for an Exotic Spin-Dependent Interaction between Electrons at the Nanometer Scale with Molecular Rulers

We propose a new scheme to constrain an exotic spin-dependent interaction between electrons at the nanometer scale. Molecular rulers containing two electron spins and a shape-persistent polymer chain are utilized in the scheme. The distances between electron spins can be tuned by varying the lengths of the polymer chains connecting the two electron spins. With the measurement of the coupling strength between electron spins, improved laboratory bounds of axial-vector mediated interaction are established in the force range from 3 to 200 nm. The upper limit of the coupling g(A)(e)g(A)(e)/4 pi(h) over barc for the force range of 200 nm is vertical bar g(A)(e)g(A)(e)/4 pi(h) over barc vertical bar <= 1.0 x 10(-12), which improves the previous limit on g(A)(e)g(A)(e)/4 pi(h) over barc by 1 order of magnitude.