Semi-flexible interacting self-avoiding trails on the square lattice

TL;DR

This paper investigates the effect of adding stiffness to the self-interacting self-avoiding trails (ISAT) model on the square lattice, finding that stiffness does not alter the collapse transition's order across a wide parameter range.

Contribution

It introduces a generalized ISAT model with stiffness on the square lattice and analyzes its phase transition behavior through computer simulations.

Findings

Stiffness does not change the order of the collapse transition for ISAT.

Large stiffness shows bimodal distributions, likely finite-size effects.

No evidence of a first-order transition at infinite stiffness within studied lengths.

Abstract

Self-avoiding walks self-interacting via nearest neighbours (ISAW) and self-avoiding trails interacting via multiply-visited sites (ISAT) are two models of the polymer collapse transition of a polymer in dilute solution. On the square lattice it has been established numerically that the collapse transition of each model lies in a different universality class. It has been shown that by adding stiffness to the ISAW model a second low temperature phase eventuates and a more complicated phase diagram ensues with three types of transition that meet at a multi-critical point. For large enough stiffness the collapse transition becomes first-order. Interestingly, a phase diagram of a similar structure has been seen to occur in an extended ISAT model on the triangular lattice without stiffness. It is therefore of interest to see the effect of adding stiffness to the ISAT model. We have studied by computer simulation a generalised model of self-interacting self-avoiding trails on the square lattice with a stiffness parameter added. Intriguingly, we find that stiffness does not change the order of the collapse transition for ISAT on the square lattice for a very wide range of stiffness weights. While at the lengths considered there are clear bimodal distributions for very large stiffness, our numerical evidence strongly suggests that these are simply finite-size effects associated with a crossover to a first-order phase transition at infinite stiffness.