Casimir-Lifshiftz Torque Enhancement by Retardation and Intervening Dielectrics

Phys. Rev. lett. 119, 183001 (2017)https://ireap.umd.edu/10.1103/PhysRevLett.119.1830012017Journal ArticleAdvanced Materials and Nanotechnology

We investigate two effects that lead to a surprising increase in the calculated Casimir-Lifshitz torque between anisotropic, planar, semi-infinite slabs. Retardation effects, which account for the finite speed of light, are generally assumed to decrease the strength of Casimir-Lifshitz interactions. However, the nonretarded approximation underestimates the Casimir-Lifshitz torque at small separations by as much as an order of magnitude. Also, Casimir-Lifshitz forces are typically weakened with the insertion of an intervening dielectric. However, a dielectric medium can increase the short-range Casimir-Lifshitz torque by as much as a factor of 2. The combined effects of retardation and an intervening dielectric dramatically enhance the Casimir-Lifshitz torque in the experimentally accessible regime and should not be neglected in calculation or experimental design.