Colloidal dynamics in artificial particle ice systems
[eng] Geometrical frustration is a general phenomenon influencing the behavior of diverse natural systems across different length scales. Geometrical frustration arises when the symmetry of the interaction among building blocks and the system geometry do not match. This incompatibility generates a sys...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/211040 |
| Acceso en línea: | https://hdl.handle.net/2445/211040 http://hdl.handle.net/10803/690834 |
| Access Level: | acceso abierto |
| Palabra clave: | Col·loides Geometria Magnetisme Matèria condensada tova Colloids Geometry Magnetism Soft condensed matter |
| Sumario: | [eng] Geometrical frustration is a general phenomenon influencing the behavior of diverse natural systems across different length scales. Geometrical frustration arises when the symmetry of the interaction among building blocks and the system geometry do not match. This incompatibility generates a system with competing interactions that are the in charge of generating a rich phenomenology. In systems where geometrical frustration is present, we may have a degenerate ground state at zero temperature, a rich phase diagram or intrinsic disorder. Nowadays, with the technological advances, scientists can construct artificial frustrated systems. Those present the potential to become materials with engineered properties or be used as a tool to further comprehend the nature of this exotic phenomena. In this thesis, I used an Artificial Colloidal Ice (ACI) as a model system to study the geometric frustration in systems with a spin degree of freedom. Colloidal particles are the interacting units of an ACI and present the advantage of having accessible time and length scales. In addition, colloidal particles have demonstrated the capability to behave as model system for atoms or molecules, both systems at length scales that are more difficult to observe. To complete this investigation, I used numerical simulations using the LAMMPS molecular dynamics simulator and experimental realizations. For the experimental realizations, I used video optical microscopy, state-of-art lithography techniques and holographic optical tweezers. This thesis presents the result of four projects that study the ACI system under different conditions, under the form of four publications accompanied by an introductory part. In the first one, I studied the effects on an ACI if the boundaries of the system are fixed. We observed that the boundaries can influence the bulk behavior; and in particular that, antiferromagnetic boundaries can reach a full ground state of the system, not possible with other types of boundaries. In the second project, I computed the colloidal and latice parameters to achieve an extensive degeneracy in a square ACI. In here, I observed a reentrant behavior: the system starting from a disordered configuration reaches a low-energy state to then achieve disorder again. The third project, studied the effects of changing the geometry of an ACI without altering its topology. I observed that excitations of the ground state with opposite topological charges can be accumulated in a certain sublatice of a mixed coordination latice or be balanced. Filling the gap among ACI and natural systems. Finally, In the fourth project, I investigated the low-energy states of a Cairo ACI, a latice made of irregular pentagons. The Cairo ACI presents a high degree of degeneracy, exhibiting a disordered ensemble at low-energy states that corresponds with a frustrated antiferrotoroid. |
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