Probing Anomalous Longitudinal Fluctuations of the Interacting Bose Gas via Bose-Einstein Condensation of Magnons

TL;DR

This paper provides exact theoretical results for the behavior of staggered spin fluctuations in quantum antiferromagnets under magnetic fields, revealing a controllable critical continuum in the longitudinal dynamic structure factor.

Contribution

It introduces a non-perturbative approach to analyze the infrared behavior of the interacting Bose gas in quantum antiferromagnets, connecting Bose-Einstein condensation of magnons to observable spin fluctuation spectra.

Findings

Longitudinal dynamic structure factor exhibits a critical continuum.

The weight of the continuum can be tuned by the magnetic field.

Results are valid for dimensions 1 < D <= 3.

Abstract

The emergence of a finite staggered magnetization in quantum Heisenberg antiferromagnets subject to a uniform magnetic field can be viewed as Bose-Einstein condensation of magnons. Using non-perturbative results for the infrared behavior of the interacting Bose gas, we present exact results for the staggered spin-spin correlation functions of quantum antiferromagnets in a magnetic field at zero temperature. In particular, we show that in dimensions 1 < D <= 3 the longitudinal dynamic structure factor S_parallel(q,omega) describing staggered spin fluctuations in the direction of the staggered magnetization exhibits a critical continuum whose weight can be controlled experimentally by varying the magnetic field.