Andreev bound states in iron pnictide superconductors

Andreev bound states have been proposed as an experimental probe to detect the pairing symmetry in iron pnictide superconductors. However, previous theoretical studies show that the local density of states below the superconducting gap is small, making the detection rather challenging in experiments. We revisit this important issue from the Bogoliubov-de Gennes Hamiltonian and carefully include both the lattice effects and the boundary potentials. It is rather surprising that significant spectral weights in the midgap regime emerge, leading to easy detection for the Andreev bound states in realistic experiments. Furthermore, pronounced peaks appear in the momentum-resolved local density of states and enhance quasiparticle interferences at specific momenta. We analyze the locations of these magic spots from quasiparticle interferences and propose a direct experimental verification by the Fourier-transformed scanning tunneling spectroscopy.