3D-melting features of the irreversibility line in overdoped Bi${}_2$Sr${}_2$CuO${}_6$ at ultra-low temperature and high magnetic field

We have measured the irreversible magnetization of an overdoped Bi${}_2$Sr${}_2$CuO${}_6$ single crystal up to B=28 T and down to T=60 mK, and extracted the irreversibility line $B_{\mathrm{i}\mathrm{r}\mathrm{r}}(T)$: the data can be interpreted in the whole temperature range as a 3D-anisotropic vortex lattice melting line with Lindemann number $c_{\mathrm{L}}=0.13$. We also briefly discuss the applicability of alternative models such as 2D- and quantum melting, and the connection with magnetoresistance experiments.