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Momoi T.,RIKEN | Sindzingre P.,CNRS Laboratory of Theoretical Physics and Condensed Matter | Kubo K.,Aoyama Gakuin University
Physical Review Letters | Year: 2012

We figure out that the ground state of a multiple-spin exchange model applicable to thin films of solid He3 possesses an octahedral spin nematic order. In the presence of a magnetic field, it is deformed into an antiferroquadrupolar order in the perpendicular spin plane, in which lattice Z 3 rotational symmetry is also broken. Furthermore, this system shows a narrow magnetization plateau at half, m/m sat=1/2, which resembles recent magnetization measurements. © 2012 American Physical Society. Source

Perera A.,CNRS Laboratory of Theoretical Physics and Condensed Matter
Molecular Physics | Year: 2011

The radial distribution function of liquid water, as obtained by the computer simulations of several classical models of water, is re-examined herein and shown to display two intriguing features. These consist of a compact three-peaks structure over three molecular diameters, which is followed by an apparent loss of the packing correlations beyond R c ≈ Å. This is in contrast to simple liquids for which the correlationsdecay continuously with distance. This structure is reproduced for many widely used classical force field models of water and by scattering experiments as well. It is also preserved in aqueous binary mixtures of organic solvents, even up to equimolar mixture in some cases. The analysis of the structure factor highlights the role played by the competition between the packing effect and the hydrogen bonding interactions. This analysis, in terms of competition of two length scales, is also supported by a simple core-soft model, which reproduces the structural features outlined above. © 2011 Copyright Taylor and Francis Group, LLC. Source

Charbonneau P.,Duke University | Tarjus G.,CNRS Laboratory of Theoretical Physics and Condensed Matter
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

We show that, in the equilibrium phase of glass-forming hard-sphere fluids in three dimensions, the static length scales tentatively associated with the dynamical slowdown and the dynamical length characterizing spatial heterogeneities in the dynamics unambiguously decorrelate. The former grow at a much slower rate than the latter when density increases. This observation is valid for the dynamical range that is accessible to computer simulations, which roughly corresponds to that accessible in colloidal experiments. We also find that, in this same range, no one-to-one correspondence between relaxation time and point-to-set correlation length exists. These results point to the coexistence of several relaxation mechanisms in the dynamically accessible regime of three-dimensional hard-sphere glass formers. © 2013 American Physical Society. Source

Essafi K.,CNRS Laboratory of Theoretical Physics and Condensed Matter | Kownacki J.-P.,Cergy-Pontoise University | Mouhanna D.,CNRS Laboratory of Theoretical Physics and Condensed Matter
Physical Review Letters | Year: 2011

Anisotropic D-dimensional polymerized phantom membranes are investigated within a nonperturbative renormalization group framework. One focuses on the transition between a high-temperature, crumpled phase and a low-temperature, tubular phase where the membrane is flat along one direction and crumpled along the other ones. While the upper critical dimension-Duc=5/2-is close to D=2, the weak-coupling perturbative approach is qualitatively and quantitatively wrong. We show that our approach is free of the problems encountered within the perturbative framework and provides physically meaningful critical quantities. © 2011 American Physical Society. Source

Leonard F.,CNRS Laboratory of Theoretical Physics and Condensed Matter | Delamotte B.,CNRS Laboratory of Theoretical Physics and Condensed Matter
Physical Review Letters | Year: 2015

We present models where γ+ and γ-, the exponents of the susceptibility in the high- and low-temperature phases, are generically different. In these models, continuous symmetries are explicitly broken down by discrete anisotropies that are irrelevant in the renormalization-group sense. The Zq-invariant models are the simplest examples for two-component order parameters (N=2) and the model with icosahedral symmetry for N=3. We accurately compute γ+-γ- as well as the ratio ν/ν′ of the exponents of the two correlation lengths present for T Source

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