Surface critical exponents for a three-dimensional modified spherical model

Дата и время публикации : 1997-06-16T14:27:10Z

Авторы публикации и институты :
D. M. Danchev (Institute of Mechanics, Bulgarian Academy of Sciences)
J. G. Brankov (Institute of Mechanics, Bulgarian Academy of Sciences)
M. E. Amin (Institute of Mechanics, Bulgarian Academy of Sciences)

Ссылка на журнал-издание: Ссылка на журнал-издание не найдена
Коментарии к cтатье: 15 pages LATEX, no figures, uses ioplppt.sty file, to appear in J. Phys. A; related articles available on http://daniel.imbm.acad.bg
Первичная категория: cond-mat.stat-mech

Все категории : cond-mat.stat-mech

Краткий обзор статьи: A modified three-dimensional mean spherical model with a L-layer film geometry under Neumann-Neumann boundary conditions is considered. Two spherical fields are present in the model: a surface one fixes the mean square value of the spins at the boundaries at some $rho > 0$, and a bulk one imposes the standard spherical constraint (the mean square value of the spins in the bulk equals one). The surface susceptibility $chi_{1,1}$ has been evaluated exactly. For $rho =1$ we find that $chi_{1,1}$ is finite at the bulk critical temperature $T_c$, in contrast with the recently derived value $gamma_{1,1}=1$ in the case of just one global spherical constraint. The result $gamma_{1,1}=1$ is recovered only if $rho =rho_c= 2-(12 K_c)^{-1}$, where $K_c$ is the dimensionless critical coupling. When $rho > rho_c$, $chi_{1,1}$ diverges exponentially as $Tto T_c^{+}$. An effective hamiltonian which leads to an exactly solvable model with $gamma_{1,1}=2$, the value for the $nto infty $ limit of the corresponding O(n) model, is proposed too.

Category: Physics