ENFORCE · ENgineering FrustratiOn in aRtificial Colloidal icEs: degeneracy, exotic lattices and 3D states

Geometric frustration, namely the impossibility of satisfying competing interactions on a lattice, has recentlybecome a topic of considerable interest as it engenders emergent, fundamentally new phenomena and holdsthe exciting promise of delivering a new class of nanoscale devices based on the motion of magnetic charges.With ENFORCE, I propose to realize two and three dimensional artificial colloidal ices and investigate thefascinating manybody physics of geometric frustration in these mesoscopic structures. I will use these softmatter systems to engineer novel frustrated states through independent control of the single particlepositions, lattice topology and collective magnetic coupling. The three project work packages (WPs) willpresent increasing levels of complexity, challenge and ambition:(i) In WP1, I will demonstrate a way to restore the residual entropy in the square ice, a fundamental longstandingproblem in the field. Furthermore, I will miniaturize the square and the honeycomb geometries and investigate the dynamics of thermally excited topological defects and the formation of grain boundaries.(ii) In WP2, I will decimate both lattices and realize mixed coordination geometries, where the similaritybetween the colloidal and spin ice systems breaks down. I will then develop a novel annealing protocol basedon the simultaneous system visualization and magnetic actuation control.(iii) In WP3, I will realize a three dimensional artificial colloidal ice, in which interacting ferromagneticinclusions will be located in the voids of an inverse opal, and arranged to form the FCC or the pyrochlorelattices. External fields will be used to align, bias and stir these magnetic inclusions while monitoring in situtheir orientation and dynamics via laser scanning confocal microscopy.ENFORCE will exploit the accessible time and length scales of the colloidal ice to shed new light on theexciting and interdisciplinary field of geometric frustration.