# Signatures of two-step impurity mediated vortex lattice melting in Bose-Einstein Condensates

## TL;DR

This paper investigates how impurities affect the melting process of vortex lattices in rotating Bose-Einstein Condensates, revealing a two-step melting process and metastable states influenced by impurity pinning and creation history.

## Contribution

It introduces two protocols for impurity introduction and uncovers a two-step vortex lattice melting process with metastable states dependent on impurity pinning and formation history.

## Key findings

- Vortex lattice undergoes two-step melting via positional and orientational order loss.
- Impurities induce metastable vortex lattice states.
- The creation protocol influences the stability of vortex lattice states.

## Abstract

We simulate a rotating 2D BEC to study the melting of a vortex lattice in presence of random impurities. Impurities are introduced either through a protocol in which vortex lattice is produced in an impurity potential or first creating the vortex lattice in the absence of random pinning and then cranking up the (co-rotating) impurity potential. We find that for a fixed strength, pinning of vortices at randomly distributed impurities leads to the new states of vortex lattice. It is unearthed that the vortex lattice follow a two-step melting via loss of positional and orientational order. Also, the comparisons between the states obtained in two protocols show that the vortex lattice states are metastable states when impurities are introduced after the formation of an ordered vortex lattice. We also show the existence of metastable states which depend on the history of how the vortex lattice is created.