Fermi-surface mean free path from sheet resistivity
= Fermi-surface mean free path from sheet resistivity
{c}
{title2=$\ell_F=\hbar k_F/(ne^2\rho_\square)$}
For a spin-degenerate parabolic two-dimensional band, the <Drude model> gives $\tau=m^*/(ne^2\rho_\square)$ and $v_F=\hbar k_F/m^*$. Their product is the displayed mass-independent <mean free path>. A Fermi-surface transport interpretation requires a sufficiently <degenerate electron gas>; a quantum lifetime need not equal the transport relaxation time.