Biaxial surface order dynamics in calamitic nematics

Thermotropic nematic materials relax strong distortions by lowering the nematic order: theuniaxial symmetry is broken and is locally replaced by biaxial domains. We investigated the dynamicsof the nematic order near a boundary surface of an asymmetric pi-cell submitted to an external electricfield, close to the electric order reconstruction threshold. An unexpected phenomenon is observed close,but below the threshold: the biaxial order spreads on the surface inducing a consequent bulk topologicalbehaviour equivalent to the splay-bend fast transition allowed by order reconstruction at higher voltage.