Left: Maximum SFE as a function of surface density for metallicity log(Z/Z_⊙) =  − 6 (blue), −4 (purple), −2 (red), and 0 (orange). Solid and dashed curves respectively show where the zero-force (F_tot = 0) and the escape velocity (${\dot{R}}_s=v_{\mathrm{esc}}$) conditions are satisfied. The dotted curve shows the time-independent solution (Eq. (3)) for the reference value ${\mathrm{\Sigma }}_{\mathrm{crit}}=2000M_{\odot }{\mathrm{pc}}^{-2}$ used by Somerville et al. (2025). Coloured ticks mark the maximum SFE across the surface density range for each metallicity. Middle: Cloud disruption time in units of the free-fall time as a function of the cloud surface density for various metallicities as indicated in the colour bar. Solid and dashed curves respectively show where the zero-force (F_tot = 0) and the escape velocity (${\dot{R}}_s=v_{\mathrm{esc}}$) conditions are satisfied. Right: Same as the middle panel but with t_d in units of megayears.