Impurity effects on the quasiparticle spectrum of the Fulde-Ferrell-Larkin-Ovchinnikov state of a d-wave superconductor
Abstract
In a d-wave superconductor (d-SC), a unitary impurity can induce a near-zero-energy resonant peak in the local tunneling density of states (LTDOS) due to the sign change of the order parameter (OP) on the Fermi surface. If a d-SC is quasi-two-dimensional, a large parallel magnetic field can drive it into the Fulde-Ferrell-Larkin-Ovchinnikov state, with an OP also changing sign in the real space like a checkerboard pattern. This double sign change leads to very subtle effects caused by a unitary impurity in the LTDOS for two locally stable locations of the impurity.