Dimeric and dipolar ground state orders in colloidal molecular crystals

Trizac, Emmanuel; Shawish, S. El; Dobnikar, Jure

doi:10.1590/s0001-37652010000100008

Cited by 4 publications

(26 citation statements)

References 12 publications

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“…Of particular interest here is a class of charged colloidal spheres in the presence of optical trap arrays, where a wide variety of crystalline states has been reported [6][7][8][9][10][11][12]. On a two-dimensional modulated substrate, multiple charged colloids can be confined in sufficiently strong traps, and thereby form n-mers which exhibit an orientational degree of freedom.…”

Section: Introductionmentioning

confidence: 99%

“…On a two-dimensional modulated substrate, multiple charged colloids can be confined in sufficiently strong traps, and thereby form n-mers which exhibit an orientational degree of freedom. It has been established from experimental, numerical and theoretical approaches [6][7][8][9][10][11][12] that such systems may show remarkably rich orientational ordering, and lead to the formation of so called colloidal molecular crystals.…”

Section: Introductionmentioning

confidence: 99%

“…We will restrict our attention to the ground state, leaving thermal effects for further studies [13]. Under these circumstances, it has been shown that in the dipolar case (with trapped clusters each formed of two oppositely charged colloids) the resulting orientational behaviour is somehow trivial: the observed phase is made up of ABABtype stripes, where the dipoles in stripe A are aligned along the stripe (up), while those in stripe B have opposite orientation [12]. Furthermore, the stripe structure cannot be tuned by modifying the lattice constant or salt content in the solution.…”

Section: Introductionmentioning

confidence: 99%

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Colloidal ionic complexes on periodic substrates: Ground-state configurations and pattern switching

2011

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We theoretically and numerically studied ordering of "colloidal ionic clusters" on periodic substrate potentials such as those generated by optical trapping. Each cluster consists of three charged spherical colloids: two negatively and one positively charged. The substrate is a square or rectangular array of traps, each confining one such cluster. By varying the lattice constant from large to small, the observed clusters are first rodlike and form ferro- and antiferrolike phases, then they bend into a bananalike shape, and finally they condense into a percolated structure. Remarkably, in a broad parameter range between single-cluster and percolated structures, we have found stable supercomplexes composed of six colloids forming grapelike or rocketlike structures. We investigated the possibility of macroscopic pattern switching by applying external electrical fields.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Colloidal ionic complexes on periodic substrates: Ground-state configurations and pattern switching

2011

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“…It is obvious that anisotropic particles can create a wider range of distinct phases than the spherical ones. Such particles can be represented by anisotropic colloids themselves, but they can be effectively created as complexes of identical two (dimer) [4,5,6,7,8] or three (trimer) [4,5,8,9] bound particles per potential minimum of the external potential. Even the case of four particles was studied previously [8].…”

Section: Introductionmentioning

confidence: 99%

“…Even the case of four particles was studied previously [8]. Another problem is the ground-state of dipoles [6], i.e., units with two oppositely charged particles, or clusters of two negative and one positive charges [10]. The filling can be even rational [11,12].…”

Section: Introductionmentioning

confidence: 99%

Tricriticality for dimeric Coulomb molecular crystals in ground state

Travěnec,

Šamaj

2017

Preprint

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We study the ground-state properties of a system of dimers. Each dimer consists in a pair of equivalent charges at a fixed distance, immersed in a neutralizing homogeneous background. All charges interact pairwisely by Coulomb potential. The dimer centers form a two-dimensional rectangular lattice with the aspect ratio α ∈ [0, 1] and each dimer is allowed to rotate around its center. The previous numerical simulations, made for the more general Yukawa interaction, indicate that only two basic dimer configurations can appear: either all dimers are parallel or they have two different angle orientations within alternating (checkerboard) sublattices. As the dimer size increases, two second-order phase transitions, related to two kinds of the symmetry breaking in dimer's orientations, were reported. In this paper, we use a recent analytic method based on an expansion of the interaction energy in Misra functions which converges quickly and provides an analytic derivation of the critical behaviour. Our main result is that there exists a specific aspect ratio of the rectangular lattice α * = 0.71410684000071 . . . which divides the space of model's phases onto two distinct regions. If the lattice aspect ratio α > α * , we recover both types of the secondorder phase transitions and find that they are of mean-field type with the critical exponent β = 1/2. If α < α * , the phase transition associated with the discontinuity of dimer's angles on alternating sublattices becomes of first order. For α = α * , the firstand second-order phase transitions meet at the tricritical point, characterized by the different critical index β = 1/4. Such phenomenon is known from literature about the Landau theory of one-component fields, but in our two-component version the scenario is more complicated: the component which is already in the symmetry-broken state at the tricritical point also interferes and exhibits unexpectedly the mean-field singular behaviour.

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Phase behaviour of colloidal assemblies on 2D corrugated substrates

Shawish

Trizac

Dobnikar

2012

J. Phys.: Condens. Matter

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We investigate--using Monte Carlo computer simulations--the phase behaviour of dimeric colloidal molecules on periodic substrates with square symmetry. The molecules are formed in a two-dimensional suspension of like charged colloids subject to periodic external confinement, which can be experimentally realized by optical methods. We study the evolution of positional and orientational order by varying the temperature across the melting transition. We propose and evaluate appropriate order parameters as well as the specific heat capacity and show that the decay of positional correlations belongs to a class of crossover transitions while the orientational melting is a second-order phase transition.

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Dimeric and dipolar ground state orders in colloidal molecular crystals

Cited by 4 publications

References 12 publications

Colloidal ionic complexes on periodic substrates: Ground-state configurations and pattern switching

Colloidal ionic complexes on periodic substrates: Ground-state configurations and pattern switching

Tricriticality for dimeric Coulomb molecular crystals in ground state

Phase behaviour of colloidal assemblies on 2D corrugated substrates

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