Phase behaviour of colloidal assemblies on 2D corrugated substrates

TL;DR

This study uses Monte Carlo simulations to analyze how dimeric colloidal molecules on 2D square substrates transition from ordered to disordered states, revealing crossover and second-order phase transitions.

Contribution

It introduces a detailed simulation-based analysis of phase behavior and melting transitions of colloidal assemblies on periodic substrates with new order parameters.

Findings

Positional correlations decay as crossover transitions.

Orientational melting is a second-order phase transition.

Order parameters effectively characterize phase changes.

Abstract

We investigate - with Monte Carlo computer simulations - the phase behaviour of dimeric colloidal molecules on periodic substrates with square symmetry. The molecules are formed in a two-dimensional suspension of like charged colloids subject to periodic external confinement, which can be experimentally realized by optical methods. We study the evolution of positional and orientational order by varying the temperature across the melting transition. We propose and evaluate appropriate order parameters as well as the specific heat capacity and show that the decay of positional correlations belongs to a class of crossover transitions while the orientational melting is a second-order phase transition.