The anisotropy induced by defects of "random local field" type in O(n) models and suppression of the Imry-Ma inhomogeneous state

TL;DR

This paper shows that in O(n) models with defects causing anisotropic local fields, the induced anisotropy can suppress the inhomogeneous Imry-Ma state, restoring long-range order when a threshold is exceeded.

Contribution

It introduces the concept that defect-induced anisotropy in O(n) models can prevent the Imry-Ma inhomogeneous state, highlighting a new mechanism for order stability.

Findings

Effective anisotropy arises for 2<d<4 due to defect distribution.

When anisotropy exceeds a threshold, the inhomogeneous state is suppressed.

Long-range order is restored in the system under certain conditions.

Abstract

We demonstrate that in the system with anisotropic distribution of the defect-induced random local field directions in the n-dimensional space of vector order parameter with the O(n) symmetry, the defect-induced effective anisotropy arises for the space dimensionality 2<d<4. If the anisotropy constant exceeds the threshold value, then an inhomogeneous state predicted by Imry and Ma becomes energetically unfavorable, and the system goes back to the state with the long-range order.