Lattice symmetries and the topological protected transport of colloidal particles

Abstract

The topologically protected transport of colloidal particles on top of magnetic patterns of all possible single lattice constant two dimensional magnetic point group symmetries is studied experimentally, theoretically, and with numerical simulations. We examine the transport of colloidal particles in response to modulation loops of the external field. We classify the modulation loops into topologically distinct classes causing different transport. We show that the lattice symmetry has a profound influence on the transport modes, the accessibility of transport networks, and the individual addressability of paramagnetic versus diamagnetic colloidal particles. We show how the transport of colloidal particles above a two fold symmetric stripe pattern changes from universal adiabatic transport at large elevations via a topologically protected ratchet motion at intermediate elevations toward a non-transport regime at low elevations. Transport above four fold symmetric patterns is closely related to the transport above two fold symmetric patterns. There exists a family of three fold symmetric patterns that vary as a function of the phase of the pattern. We show how this family can be divided into two topologically distinct classes supporting different transport modes and being protected by proper and improper six fold symmetries. Both classes support individual control over the transport of paramagnetic and diamagnetic particles. We discuss the topological transition when moving the phase from one class of pattern to the other class. The similarities and the differences in the lattice symmetry protected transport of classical over-damped colloidal particles versus the topologically protected transport in quantum mechanical systems are emphasized