Holstein polarons and triplet bipolarons with NNN hopping

TL;DR

This paper investigates the effects of next nearest neighbour hopping on 1D Holstein polarons and triplet bipolarons, revealing shifts in band minima and differences from SSH polarons through variational and diagonalization methods.

Contribution

It introduces a variational approach to study NNN hopping effects on Holstein polarons and bipolarons, highlighting differences from SSH models.

Findings

Polaron band minima can occur at non-zero momentum depending on NNN hopping sign and magnitude.

Differences between Holstein and SSH polarons are clarified through comparative analysis.

Triplet bipolarons exhibit distinct behavior influenced by extended Hubbard interactions.

Abstract

We study the ground state of 1D Holstein single polaron with next nearest neighbour electron hopping (NNN), employing a variational approximation based on exact diagonalization. Our investigation reveals that, depending upon the sign and magnitude of the NNN hopping integral with respect to nearest neighbour hopping, the polaron band minima may occur at non-zero kGS. We compare the present scenario with the SSH polarons, where a similar feature is also observed, albeit, due to very different mechanism. Our initial investigation of triplet bipolarons, in presence of an attractive extended Hubbard interactions, further substantiates the differences between the present model and the SSH model.