Signatures of two-step impurity-mediated vortex lattice melting in Bose-Einstein condensates Thudiyangal Mithun, Somesh Chandra Ganguli, Pratap Raychaudhuri and Bishwajyoti Dey EPL, 123 2 (2018) 20004 Published online: 20 August 2018 DOI: 10.1209/0295-5075/123/20004