Comment on "Quantum Melting of the Quasi-Two-Dimensional Vortex Lattice in $κ-(ET)_2Cu(NCS)_2$"

Abstract

In a recent Letter Mola et al. \cite{mola} reported magnetization measurements $M(H,θ)$ performed on the organic superconductor $κ-$(ET)$_2$Cu(NCS)$_2 (T_c = 9.1$ K) as a function of the magnetic field $H$ applied at different angles $θ$ with respect to the $a$-axis direction. The results \cite{mola} demonstrate: (a) the occurrence of pronounced irreversible magnetization $M_{\rm irr}(H)$ jumps and (b) their sudden cessation for $H \ge H_m(T,θ)$. The boundary line $H_m(T)$ has been interpreted by Mola et al. as the Q2D vortex lattice (VL) quantum melting phase transition line \cite{mola}. The purpose of this comment is to show that the results can be understood in a simple way without invoking "quantum melting phase transition".