SUBSTITUTIONAL DISORDER IN A FIBONACCI CHAIN - RESONANT EIGENSTATES AND INSTABILITY OF THE SPECTRUM

The effect of substitutional disorder in a Fibonacci chain is studied. In particular it is shown that the presence of a single impurity affe cts all the states of the unperturbed system, reducing the fractal dim ension of the spectrum. Resonant eigenstates are also observed. The co nsequences of the instability of the spectrum are discussed in the con text of the experimental electronic measurements and also the effect o f boundary conditions in theoretical calculations.