arXiv subjects

J. M. Yeomans

Publications and source records attributed to J. M. Yeomans.

76 records · Page 5Linked to original sources

arXiv1994

Quantum Fluctuations in the Annni Model

We obtain the ANNNI model from a Heisenberg model with large single--ion anisotropy energy, $D$, as might be relevant for helical spin systems. We treat quantum fluctuations to lowest order in $1/S$ at zero temperature within an expansion in $J/D$, where $J$ is an exchange energy. The transition from the state with periodicity $p=4$ to the uniform state ($p= \infty$) occurs via an infinite sequence of first order transitions in which $p$ increases monotonically.

cond-mat↗

arXiv1994

The Role of Spin Anisotropy in the Unbinding of Interfaces

We study the ground state of a classical X-Y model with $p \ge 3$-fold spin anisotropy $D$ in a uniform external field, $H$. An interface is introduced into the system by a suitable choice of boundary conditions. For large $D$, as $H \to 0$, we prove using an expansion in $D^{-1}$ that the interface unbinds from the surface through an infinite series of layering transitions. Numerical work shows that the transitions end in a sequence of critical end points.

cond-mat↗

arXiv1994

Spin Softening in Models with Competing Interactions: A New High Anisotropy Expansion to All Orders

An expansion in inverse spin anisotropy, which enables us to study the behaviour of discrete spin models as the spins soften, is developed. In particular we focus on models, such as the chiral clock model and the $p$-state clock model with competing first and second neighbour interactions, where there are special multiphase points at zero temperature at which an infinite number of ground states are degenerate. The expansion allows calculation of the ground state phase diagram near these points as the spin anisotropy, which constrains the spin to take discrete values, is reduced from infinity. Several different behaviours are found, from a single first order phase boundary to infinite series of commensurate phases.

cond-mat↗

arXiv1994

Wetting on Lines and Lattices of Cylinders

This paper discusses wetting and capillary condensation transitions on a line and a rectangular array of cylinders using an interface potential formalism. For a line of cylinders, there is a capillary condensation transition followed by complete wetting if the cylinders are sufficiently close together. Both transitions disappear as the cylinder separation is increased. The dependence of the wetting phase diagram of a rectangular array of cylinders is discussed as a function of the chemical potential, substrate--fluid interaction strength and surface tension.

cond-mat↗