With respect to all,
I am workin in bilayer system seperated by a barriere for getting resistivity. I have a confusion in equation of effective dielectric function. In no of articles i have seen that e(q,w)=[1+U_2D(q)chi_2D(q,w)][....]-[....]. But There are no of articles available where e(q,w)=[1-U_2D(q)chi_2D(q,w)][....]-[....]. There is difference of sign + and -. I am not able to differentiate this and what this difference affect potential and polarisation function. When and what equation we should use.