  The Casimir interaction and torque are related phenomena originating from the
exchange of electromagnetic excitations between objects. While the Casimir
force exists between any types of objects, the materials or geometrical
anisotropy drives the emergence of the Casimir torque. Here both phenomena are
studied theoretically between dielectric films with immersed parallel single
wall carbon nanotubes in the dilute limit with their chirality and collective
electronic and optical response properties taken into account. It is found that
the Casimir interaction is dominated by thermal fluctuations at sub-micron
separations, while the torque is primarily determined by quantum mechanical
effects. This peculiar quantum vs. thermal separation is attributed to the
strong influence of reduced dimensionality and inherent anisotropy of the
materials. Our study suggests that nanostructured anisotropic materials can
serve as novel platforms to uncover new functionalities in ubiquitous Casimir
phenomena.
