Odd-parity S-matrix of a symmetric double-delta potential
= Odd-parity S-matrix of a symmetric double-delta potential
{c}
{title2=$S_{--}$}
For positive <wavenumber> $k$, the odd channel of the <symmetric double-delta potential> has
$$
S_{--}(k)=e^{-2ika}
\frac{k e^{ika}+U_0\sin(ka)}{k e^{-ika}+U_0\sin(ka)}.
$$
For real $k$ its numerator and denominator are complex conjugates, making the channel <unitary operator>[unitary]. Its poles are the zeros of $k e^{-ika}+U_0\sin(ka)$.