Effects of higher order excitations on the bandgap narrowing of quantum wires

The effects of higher order excitations on the bandgap renormalization of quasi-one dimensional semiconductor systems within the dynamical random phase approximation is studied. the contribution of the first and second excited states wave functions is incorporated in the calculation of the bandgap narrowing due to many-body exchange-correlation effects. it is shown that incorporation of the higher order excitations leads to the result that absolute values of the bandgap narrowing in these cases are larger than the corresponding renormalization which is calculated by only considering the ground state wave function.