Resonant Tunneling States of a Pairing Ladder with Random Dimer Chains

We propose three models of pairing ladders, in which two types of atoms, A and B, exist, and the corresponding atoms in different chains are pairng, i.e. if atom A is in a site of one chain, the atom in the corresponding site of another chain should be atom B. It is found that there are three resonant states in the ladder when the two types of atoms are both random dimers (RD) in the same chain. No extended state exists in the ladder when only one type of atom is RD distributed or two types of atoms both are random distributed in the same chain.