Comment on "Quantum Melting of the Quasi-Two-Dimensional Vortex Lattice in $\kappa -(ET{)}_{2}Cu(NCS{)}_2$"

Abstract

In a recent Letter Mola et al. \cite{mola} reported magnetization measurements $M(H,\theta )$ performed on the organic superconductor $\kappa -$(ET)${}_2$Cu(NCS)${}_2(T_c=9.1$ K) as a function of the magnetic field $H$ applied at different angles $\theta$ with respect to the $a$-axis direction. The results \cite{mola} demonstrate: (a) the occurrence of pronounced irreversible magnetization $M_{\mathrm{irr}}(H)$ jumps and (b) their sudden cessation for $H\ge H_m(T,\theta )$. 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".

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