The Low-Field Critical End Point of the First Order Transition Line in YBCO

TL;DR

This paper uses simulations to identify a critical end point in the phase transition of YBCO at low magnetic fields, revealing a transition between two vortex liquid states with distinct short-range orders.

Contribution

It demonstrates that the first order transition line in YBCO ends at a critical point at low fields, not related to vortex lattice melting, using Lawrence-Doniach model simulations.

Findings

Magnetization discontinuity vanishes at the critical end point.

Transition separates two vortex liquid states with different short-range order.

Results agree with experimental observations.

Abstract

We report on simulations of the first order phase transition in YBCO using the Lawrence-Doniach model. We find that the magnetization discontinuity vanishes and the first order transition line ends at a critical end point for low magnetic fields in agreement with experiment. The transition is not associated with vortex lattice melting, but separates two vortex liquid states characterized by different degrees of short-range crystalline order and different length scales of correlations between vortices in different layers.