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Collective Directional Locking of Colloidal Monolayers on a Periodic Substrate.
Ralph L Stoop1, Arthur V Straube1,2,3, Tom H Johansen4,5
1Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain.
Physical Review Letters
|February 22, 2020
Summary
Collective effects in paramagnetic colloidal particles create directional locking and transversal currents when driven across a magnetic bubble lattice. This phenomenon, driven by a rotating magnetic field, can be controlled with an additional bias field.
Area of Science:
- Soft matter physics
- Colloidal science
- Non-equilibrium statistical mechanics
Background:
- Paramagnetic colloidal particles are utilized in micro- and nanotechnologies.
- Driven colloidal systems exhibit complex emergent behaviors.
- Lattice structures provide a platform for studying particle transport phenomena.
Purpose of the Study:
- To investigate directional locking effects in a monolayer of paramagnetic colloidal particles.
- To understand the role of collective particle behavior in directed transport.
- To explore the influence of lattice symmetry and driving fields on particle dynamics.
Main Methods:
- Utilizing a triangular lattice of magnetic bubbles.
- Applying an external rotating magnetic field to create a 2D traveling wave ratchet.
- Observing particle transport and collective dynamics at varying densities.
- Employing an additional bias field to influence transport direction.
Main Results:
- Single particles do not exhibit directional preference.
- High particle densities lead to spontaneous symmetry breaking, inducing transversal current and directional locking.
- An external bias field can polarize the colloidal current, favoring specific transport directions.
- The observed phenomena are linked to the interplay between particle-particle interactions and the underlying lattice potential.
Conclusions:
- Collective behavior is crucial for achieving directional transport in driven colloidal systems.
- The triangular magnetic bubble lattice serves as a tunable platform for studying symmetry breaking and directional locking.
- Controlling colloidal transport via external fields opens possibilities for micro-robotic and directed self-assembly applications.
