Strongly Asymmetric Tricriticality of Quenched Random-Field Systems

TL;DR

This study uses renormalization-group analysis to show that quenched random fields significantly alter the tricritical behavior of the 3D spin-1 Ising model, transforming first-order transitions into second-order and creating an asymmetric phase diagram.

Contribution

It reveals that quenched random fields have a stronger effect than random bonds, inducing reentrant behavior and extreme asymmetry in the tricritical phase diagram.

Findings

Random fields convert first-order to second-order transitions.

The phase diagram exhibits extreme asymmetry and reentrance.

The tricritical exponent $eta_u$ is unusually small.

Abstract

In view of the recently seen dramatic effect of quenched random bonds on tricritical systems, we have conducted a renormalization-group study on the effect of quenched random fields on the tricritical phase diagram of the spin-1 Ising model in $d=3$. We find that random fields convert first-order phase transitions into second-order, in fact more effectively than random bonds. The coexistence region is extremely flat, attesting to an unusually small tricritical exponent $\beta_u$; moreover, an extreme asymmetry of the phase diagram is very striking. To accomodate this asymmetry, the second-order boundary exhibits reentrance.