Alkali-metal adsorbate polarization on conducting and insulating surfaces probed with Bose-Einstein condensates

A magnetically trapped ${}^{87}\mathrm{Rb}$ Bose-Einstein condensate is used as a sensitive probe of short-range electrical forces. In particular, the electric polarization of, and the subsequent electric field generated by, ${}^{87}\mathrm{Rb}$ adsorbates on conducting and insulating surfaces is measured by characterizing perturbations to the magnetic trapping potential using high quality factor condensate excitations. The nature of the alterations to the electrical properties of $\mathrm{Rb}$ adsorbates is studied on titanium (metal) and silicon (semiconductor) surfaces, which exhibit nearly identical properties, and on glass (insulator), which displays a smaller transitory electrical effect. The limits of this technique in detecting electrical fields and ramifications for measurements of short-range forces near surfaces are discussed.