Absence of hole pairing in a simple t-J model on the Shastry-Sutherland lattice

TL;DR

This study investigates the doped Shastry-Sutherland model using exact diagonalization, finding that hole pairing does not occur despite the presence of a spin gap, with holes remaining strongly repulsive at moderate doping levels.

Contribution

It provides the first detailed analysis of hole doping effects in the Shastry-Sutherland model, revealing the absence of hole pairing in this frustrated spin system.

Findings

Diagonal dimer order persists at moderate doping.

Holes are strongly repulsive unless hopping is very small.

Spin gap does not lead to hole pairing in this model.

Abstract

The Shastry-Sutherland model is a two-dimensional frustrated spin model whose ground state is a spin gap state. We study this model doped with one and two holes on a 32-site lattice using exact diagonalization. When t'>0, we find that the diagonal dimer order that exists at half-filling are retained at these moderate doping levels. No other order is found to be favored on doping. The holes are strongly repulsive unless the hopping terms are unrealistically small. Therefore, the existence of a spin gap at half-filling does not guarantee hole-pairing in the present case.