Spin polaron in the J1-J2 Heisenberg model

TL;DR

This study investigates the validity of the spin polaron concept in the frustrated J1-J2 Heisenberg model by analyzing spectral functions across different magnetic phases using advanced computational methods.

Contribution

It provides a comprehensive analysis of the spin polaron quasiparticle in various phases, including disordered states, using self-consistent Born approximation and Lanczos diagonalization.

Findings

Spin polaron quasiparticles are well-defined in ordered phases near quantum critical points.

Frustration increases multimagnon contributions, reducing quasiparticle coherence.

The validity of the spin polaron picture in disordered phases is discussed based on numerical results.

Abstract

We have studied the validity of the spin polaron picture in the frustrated J1-J2 Heisenberg model. For this purpose, we have computed the hole spectral functions for the Neel, collinear, and disordered phases of this model, by means of the self-consistent Born approximation and Lanczos exact diagonalization on finite-size clusters. We have found that the spin polaron quasiparticle excitation is always well defined for the magnetically ordered Neel and collinear phases, even in the vicinity of the magnetic quantum critical points, where the local magnetization vanishes. As a general feature, the effect of frustration is to increase the amplitude of the multimagnon states that build up the spin polaron wave function, leading to the reduction of the quasiparticle coherence. Based on Lanczos results, we discuss the validity of the spin polaron picture in the disordered phase.