73,956 research outputs found
Phase Transitions with Discrete Symmetry Breaking in Antiferromagnetic Heisenberg Models on a Triangular Lattice
We study phase transition behavior of the Heisenberg model on a distorted
triangular lattice with competing interactions. The ground-state phase diagram
indicates that underlying symmetry can be changed by tuning parameters. We
focus on two cases in which a phase transition with discrete symmetry breaking
occurs. The first is that the order parameter space is SO(3). In
this case, a first-order phase transition, with threefold symmetry breaking,
occurs. The second has the order parameter space SO(3). In this
case, a second-order phase transition occurs with twofold symmetry breaking. To
investigate finite-temperature properties of these phase transitions from a
microscopic viewpoint, we introduce a method to make the connection between
continuous frustrated spin systems and the Potts model with invisible states.Comment: 5 pages, 2 figure
Structural transitions of monoolein bicontinuous cubic phase induced by inclusion of protein lysozyme solutions
Inclusion of protein lysozyme molecules in lipidic monoolein cubic phase
induces a transition from a structure to one.
Small-angle X-ray scattering (SAXS) method with high intensity synchrotron
radiation enabled us to follow closely the transition depending on the
conditions of lysozyme solutions. We showed that concentrated lysozyme
solutions induced the appearance of the structure coexisting
with the structure. From the relation between the lattice
parameters of these two structures it was shown that they were related by the
Bonnet transformation of underlying triply periodic minimal surfaces. We found
that the transition also occurred at lower lysozyme concentration when NaCl
induced attraction between lysozyme molecules. The origin of the transition was
considered as a frustration in the cubic phase where lysozyme molecules were
highly confined. A simple estimation of the frustration was given, which took
into account of the translational entropy of lysozyme molecules. At the highest
concentration of lysozyme and NaCl the structure was found to
disappear and left only the structure. This was probably
either due to the crystallization or phase separation of lysozyme solutions
ongoing microscopically, which absorbed lysozyme molecules from channels of the
cubic phase and thus removed the frustration.Comment: 8 pages, 5 figure
Slow Relaxation Process in Ising like Heisenberg Kagome Antiferromagnets due to Macroscopic Degeneracy in the Ordered State
We study relaxation phenomena in the ferromagnetically ordered state of the
Ising-like Heisenberg kagome antiferromagnets. We introduce the "weathervane
loop" in order to characterize macroscopic degenerate ordered states and study
the microscopic mechanism of the slow relaxation from a view point of the
dynamics of the weathervane loop configuration. This mechanism may give a
possible origin of the slow relaxation reported in recent experiments.Comment: 6pages, 4figures, HFM2006 proceeding
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