Electric field induced order reconstruction in a nematic cell.
We have experimentally observed the biaxial switching between two topologically distinct textures of a nematic liquid crystal cell submitted to a strong electric field. The effect is deduced from optical and electrical measurements across the cell. Above a static threshold, a bulk order reconstruction is observed, where the final nematic orientation in the centre becomes perpendicular to its initial one, inducing a total pi change of orientation across the cell. Using short electric field pulses, a higher dynamical threshold is observed. These experiments are explained by a Landau-de Gennes-Khalatnikov model. The threshold implies the local exchange of two eigenvalues of the nematic order tensor through intermediate biaxial states. The onset of the effect in a thin splay-bend wall decreases the static threshold by almost an order of magnitude. The model explains reasonably well the static and dynamic measurements within the present description of nematic biaxiality.
Barberi
R
R
Dipartimento di Fisica, Istituto Nazionale di Fisica della Materia, Universitá di Calabria, Rende, 87036, Cosenza, Italy.
Ciuchi
F
F
Durand
G E
GE
Iovane
M
M
Sikharulidze
D
D
Sonnet
A M
AM
Virga
E G
EG
D004560:Electricity; D004563:Electrochemistry; D004574:Electromagnetic Fields; D008962:Models, Theoretical; D011108:Polymers / Q000737:chemistry; D013696:Temperature; D013997:Time Factors
D011108:Polymers; C422409:liquid crystal polymer