23 research outputs found
The enhancement of ferromagnetism in uniaxially stressed diluted magnetic semiconductors
We predict a new mechanism of enhancement of ferromagnetic phase transition
temperature in uniaxially stressed diluted magnetic semiconductors (DMS)
of p-type. Our prediction is based on comparative studies of both Heisenberg
(inherent to undistorted DMS with cubic lattice) and Ising (which can be
applied to strongly enough stressed DMS) models in a random field approximation
permitting to take into account the spatial inhomogeneity of spin-spin
interaction. Our calculations of phase diagrams show that area of parameters
for existence of DMS-ferromagnetism in Ising model is much larger than that in
Heisenberg model.Comment: Accepted for publication in Phys. Rev.
Levy targeting and the principle of detailed balance
We investigate confined L\'{e}vy flights under premises of the principle of
detailed balance. The master equation admits a transformation to L\'{e}vy -
Schr\"{o}dinger semigroup dynamics (akin to a mapping of the Fokker-Planck
equation into the generalized diffusion equation). We solve a stochastic
targeting problem for arbitrary stability index of L\'{e}vy drivers:
given an invariant probability density function (pdf), specify the jump - type
dynamics for which this pdf is a long-time asymptotic target. Our
("-targeting") method is exemplified by Cauchy family and Gaussian target
pdfs. We solve the reverse engineering problem for so-called L\'{e}vy
oscillators: given a quadratic semigroup potential, find an asymptotic pdf for
the associated master equation for arbitrary