Knight shifts around vacancies in the 2D Heisenberg model

TL;DR

This paper investigates the local magnetic response around vacancies in a 2D spin-1/2 Heisenberg antiferromagnet using quantum Monte Carlo simulations, revealing detailed behavior of Knight shifts and impurity effects relevant for NMR and susceptibility measurements.

Contribution

It provides a detailed analysis of Knight shifts near vacancies, including uniform and staggered contributions, and predicts observable impurity susceptibility effects in large systems.

Findings

Separation of Knight shifts into uniform and staggered parts.

Long and short range behaviors of local responses.

Prediction of observable Curie impurity susceptibility in large systems.

Abstract

The local response to a uniform field around vacancies in the two-dimensional (2D) spin-1/2 Heisenberg antiferromagnet is determined by numerical quantum Monte Carlo simulations as a function of temperature. It is possible to separate the Knight shifts into uniform and staggered contributions on the lattice which are analyzed and understood in detail. The contributions show interesting long and short range behavior that may be of relevance in NMR and susceptibility measurements. For more than one impurity remarkable non-linear enhancement and cancellation effects take place. We predict that the Curie impurity susceptibility will be observable for a random impurity concentration even in the thermodynamic limit.