# Near-Boundary and Bulk Regions of a Semi-Infinite Two-Dimensional Heisenberg Antiferromagnet

## TL;DR

This paper analyzes the elementary excitations in a semi-infinite 2D Heisenberg antiferromagnet, revealing boundary and bulk modes, and shows boundary effects enhance nearest-neighbor spin correlations at the edge.

## Contribution

It introduces a detailed spin-wave analysis distinguishing boundary and bulk excitations, highlighting boundary-induced modifications in spin correlations.

## Key findings

- Boundary spin waves eject bulk modes from edges
- Edge spin correlations exceed bulk values
- Boundary effects significantly alter local magnetic properties

## Abstract

Using the spin-wave approximation elementary excitations of a semi-infinite two-dimensional $S=\frac12$ Heisenberg antiferromagnet are considered. The spectrum consists of bulk modes -- standing spin waves and a quasi-one-dimensional mode of boundary spin waves. These latter excitations eject bulk modes from two boundary rows of sites, thereby dividing the antiferromagnet into two regions with different dominant excitations. As a result absolute values of nearest-neighbor spin correlations on the edge exceed the bulk value.