Phase fluctuations versus Gaussian fluctuations in optimally-doped YBa${}_2$Cu${}_3$O${}_7$

Lu Li, Yayu Wang, N. P. Ong

We analyze recent torque measurements of the magnetization $M_d$ vs. magnetic field $H$ in optimally doped YBa${}_2$Cu${}_3$O${}_{7-y}$ (OPT YBCO) to argue against a recent proposal by R…