COMPLEX-BARRIER TUNNELING TIMES

In this paper we calculate the analytic expression of the phase time f or the scattering of an electron off a complex square barrier. As is w ell known the (negative) imaginary part of the potential takes into ac count, phenomenologically, the absorption. We investigate the Hartman- Fletcher effect, and find that it is suppressed by the presence of a ( non negligible) imaginary potential. In fact, when a sufficiently larg e absorption is present, the asymptotical transmission speed is finite . Actually, the tunnelling time does increase linearly with the barrie r width. A recent optical experiment seems to be in agreement with our theoretical expectation.