Localization length at a step Dirac mass wall
= Localization length at a step Dirac mass wall
{c}
{title2=$\xi_\pm=\hbar c/|V_\pm|$}
When the mass is constant $V_+>0$ above the wall and $V_-<0$ below it, amplitude decay lengths are $\xi_+=\hbar c/V_+$ and $\xi_-=\hbar c/|V_-|$. A scalar transverse envelope multiplying a unit <spinor> has normalization $\sqrt{2/(\xi_++\xi_-)}$. Density decays twice as fast as amplitude.