Phase transition in finite systems of 3D planar spin model with modified potential

We have studied the 3D planar spin model with modified potential using micro-canonical Monte Carlo simulations. For the first time, we have determined the value of q to be ⩾7.5 for the system to undergo a first-order transition. We have determined the negative specific heat and transition width as a function of system size at the first-order transition. The results have been compared with that of 2D Potts model and the 2D planar spin model with modified potential. The negative specific heat and the transition width at the first-order transition are found to be almost constant with increase in system size; unlike the 2D systems. The results have been understood qualitatively, in terms of order parameter correlation radius and correlation function.