Observation of smectic-Aordering in a solution of rigid-rod-like particles

We present experimental evidence of the smectic-A (SA) phase in colloidal solutions of tobacco mosaic virus. The smectic-A phase is determined by the observation of a layered structure along the virus alignment direction and a liquidlike order within layers. In our samples, we also observed the characteristic SA-type focal conic textures and in-layer undulational fluctuations. Our observations confirm the predictions from computer simulations and theory of smectic-A order in the system of hard rods.