Polarization dependence of spin excitations in BaCu2Si2O7

TL;DR

This study investigates how magnetic excitations in BaCu2Si2O7 depend on polarization, comparing experimental neutron scattering data with theoretical models, revealing good agreement for transverse but not longitudinal spin fluctuations due to RPA limitations.

Contribution

The paper provides a detailed comparison of polarization-dependent spin excitations in BaCu2Si2O7 with theoretical models, highlighting the limitations of RPA in capturing longitudinal fluctuations.

Findings

Quantitative agreement for transverse spin fluctuations.

Discrepancies for longitudinal polarization due to RPA limitations.

Intrinsic correlation effects are significant in longitudinal excitations.

Abstract

The polarization dependence of magnetic excitations in the quasi one-dimensional antiferromagnet BaCu2Si2O7 is studied as a function of momentum and energy transfer. The results of inelastic neutron scattering measurements are directly compared to semi-analytical calculations based on the chain-Mean Field and Random Phase approximations. A quantitative agreement between theoretically calculated and experimentally measured dynamic structure factors of transverse spin fluctuations is obtained. In contrast, substantial discrepancies are found for longitudinal polarization. This behavior is attributed to intrinsic limitations of the RPA that ignores correlation effects.