ELECTRIC-FIELD-INDUCED ISOTROPIC-NEMATIC PHASE-TRANSITION

We measure optically the quadrupolar order S induced by a stabilizing electric field E in the isotropic phase of the nematogenic 4'-n-pentyl-4-cyanobiphenyl, with large positive dielectric anisotropy epsilon(a) approximately 10. For high enough field and low enough temperaure, a paranematic-nematic first-order transition is induced, with a critical point at E(c) = 1.41 X 10(5) V/cm, T(c) = T(NI) + 0.65 K, and S(c) = 0.15, where T(NI) is the nematic-isotropic phase-transition temperature.