Andreev bound states in iron pnictide superconductors

Abstract

Recently, Andreev bound states in iron pnictide have been proposed as an experimental probe to detect the relative minus sign in the $s_\pm$-wave pairing. While previous theoretical investigations demonstrated the feasibility of the approach, the local density of states in the midgap regime is small, making the detection hard in experiments. We revisit this important problem from the Bogoliubov-de Gennes Hamiltonian on the square lattice with appropriate boundary conditions. Significant spectral weights in the midgap regime are spotted, leading to easy detection of the Andreev bound states in experiments. Peaks in the momentum-resolved local density of states appear and lead to enhanced quasiparticle interferences at specific momenta. We analyze the locations of these magic spots and propose they can be verified in experiments by the Fourier-transformed scanning tunneling spectroscopy.