Single hole doped strongly correlated ladder with a static impurity

Abstract

We consider a strongly correlated ladder with diagonal hopping and exchange interactions describedby a t–J type Hamiltonian. We study the dynamics of a single hole in this model in thepresence of a static non-magnetic (or magnetic) impurity. In the case of anon-magnetic (NM) impurity we solve the problem analytically both in the triplet(S = 1) andsinglet (S = 0) sectors. In the triplet sector the hole does not form any bound state with the impurity.However, in the singlet sector the hole forms bound states of different symmetries with increasingJ/t values. Binding energies of those impurity–hole bound states are compared withthe binding energy of a pair of holes in the absence of any impurity. In the caseof magnetic impurity the analytical eigenvalue equations are solved for a large(50 × 2) lattice. In this casealso, with increasing J/t values, impurity–hole bound states of different symmetries are obtained. Binding of thehole with the impurity is favoured for the case of a ferromagnetic (FM) impurity ratherthan the case of an antiferromagnetic (AFM) impurity. However, the binding energy isfound to be maximum for the NM impurity. Comparison of binding energies and variousimpurity–hole correlation functions indicates a pair-breaking mechanism by the NMimpurity.