You can't plot a complex number versus two independent variables -- you would need four axes.
What you can do is:
Use two separate figures (or two subplots in the same figure) to plot real part and imaginary part. In Matlab,
surf(T,w,real(sys2)); figure %// create new figure for the other graph surf(T,w,imag(sys2));
Alternatively, plot absolute value and phase:
surf(T,w,abs(sys2)); figure %// create new figure for the other graph surf(T,w,angle(sys2));
A more exotic possibility is to use
z
axis for absolute value and colour for phase, in the same graph:surf(T,w,abs(sys2),angle(sys2)); %// fourth argument of surf specifies colour