Scaling properties at the interface between different critical subsystems: The Ashkin-Teller model

TL;DR

This paper investigates the critical behavior at the interface between two different Ashkin-Teller models, revealing how varying couplings influence surface and bulk critical exponents through theoretical analysis and DMRG simulations.

Contribution

It introduces a study of interface critical phenomena between coupled Ashkin-Teller models with different couplings, highlighting continuous variation of exponents at the interface.

Findings

Interface critical exponents vary continuously with coupling strength.

Scaling predictions are confirmed by DMRG calculations.

Critical behavior depends on the marginal coupling regime.

Abstract

We consider two critical semi-infinite subsystems with different critical exponents and couple them through their surfaces. The critical behavior at the interface, influenced by the critical fluctuations of the two subsystems, can be quite rich. In order to examine the various possibilities, we study a system composed of two coupled Ashkin-Teller models with different four-spin couplings epsilon, on the two sides of the junction. By varying epsilon, some bulk and surface critical exponents of the two subsystems are continuously modified, which in turn changes the interface critical behavior. In particular we study the marginal situation, for which magnetic critical exponents at the interface vary continuously with the strength of the interaction parameter. The behavior expected from scaling arguments is checked by DMRG calculations.