Re-entrant Behavior and Gigantic Response in Disordered Spin-Peierls System

TL;DR

This paper investigates how disorder and external fields influence the competition between spin-Peierls and antiferromagnetic states in a disordered quasi-one-dimensional spin system, revealing re-entrant behavior and colossal response phenomena.

Contribution

It provides a theoretical analysis of the effects of disorder and external perturbations on spin-Peierls systems, highlighting re-entrant lattice distortions and large responses similar to colossal magnetoresistance.

Findings

Re-entrant spin-Peierls lattice distortions above impurity-induced antiferromagnetic phase

Weak perturbations cause drastic changes in the system's behavior

Large responses akin to colossal magnetoresistance observed

Abstract

Effects of disorder and external field on the competing spin-Peierls and antiferromagnetic states are studied theoretically in terms of the numerical transfer matrix method applied to a quasi one-dimensional spin 1/2 Heisenberg model coupled to the lattice degree of freedom. We show that, at temperatures above the impurity-induced antiferromagnetic phase, inhomogeneous spin-Peierls lattice distortions remain to exist showing a re-entrant behavior. This feature can be drastically altered by very weak perturbations, e.g., the staggered magnetic field or the change in interchain exchange coupling $J_\perp$, leading to a huge response, which is analogous to the colossal magnetoresistance phenomenon in perovskite manganese oxides.