Self-Rotation of Particles with a Photoinduced Electric Dipole Moment
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RETICAL AND MATHEMATICAL PHYSICS
Self-Rotation of Particles with a Photoinduced Electric Dipole Moment A. I. Grachev Ioffe Physical Institute, St. Petersburg, 194021 Russia e-mail: [email protected] Received March 9, 2019; revised February 3, 2020; accepted March 5, 2020
Abstract—We consider the realization of rotation of particles with a photoinduced dipole moment in the absence of an external field source. The effects considered here are based on the mechanism of the orientational interaction of at least a pair of particles that are photodipoles. We consider examples of realization of this mechanism including the geometry corresponding to the Quincke photorotation. From the point of view of applications, the variety of self-rotation in the case of a single photodipole located on or near a metal surface can be of interest. The torque for spherical particles with a radius of 10 μm is estimated. DOI: 10.1134/S1063784220080083
The effects of rotation of a spherical particle with an electric dipole moment photoinduced as a result of its continuous illumination in a static electric field were considered for the first time in [1, 2]. The geometries of the experiments described in [1, 2] differed in the orientation of induced dipole moment Pph relative to applied electric field vector Eex. In [1], vector Pph is orthogonal to Eex and the particle can rotate for any magnitude of the field, while, in [2], vectors Pph and Eex are antiparallel (Quincke rotation (QR) geometry [3, 4]). In the latter case, the rotation of a particle submerged into a viscous medium is possible only when field Eex exceeds a certain critical field Ec [4]. However, since photoinduced QR can be realized in any gaseous medium and even in vacuum [2], the value of Ec can be reduced to almost zero. The requirement of application of an external electric field can be an obstacle in the case of practical realization of the photoinduced rotation effect. In this communication, we consider the possibility of rotation of an illuminated spherical particle (photodipole) in a zero external electric field in the case in which the torque appears in it due to the electrostatic (orientational) interaction of the photodipole with at least one more particle possessing a dipole moment. An interesting variant off realization of the self-rotation mechanism is the case of a single photodiode located near or on a metal surface. This effect can be explained by the interaction of a photodipole with the charge of the surface induced by the photodipole and can serve as the basis for developing a new method of the optomechanical manipulation with micro- and nanoparticles. The effect of the dipole–dipole interaction of particles possessing a constant electric (or magnetic)
dipole moment is well known. By way of example, Fig. 1 illustrates the interaction of two electric dipoles with the centers separated by distance r (that should be treated as vector r) and moments P1 and P2 are parallel. The electric field of each dipole (E1 and E2, respectively) induces the torque of t
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