Magnetic field-induced one-magnon Raman scattering in the magnon Bose-Einstein condensation phase of TlCuCl$_{3}$

TL;DR

This study observes a one-magnon Raman peak in TlCuCl₃'s magnon Bose-Einstein condensation phase, linking Raman shift to magnon energy and intensity to magnetization, supported by theoretical Raman selection rules.

Contribution

It provides the first experimental observation of a one-magnon Raman peak in the BEC phase of TlCuCl₃ and clarifies the underlying selection rules through theoretical analysis.

Findings

Raman peak corresponds to one-magnon energy at the magnetic Γ point.

Raman intensity is proportional to squared transverse magnetization.

Theoretical Raman selection rules match experimental observations.

Abstract

We report the observation of the $A_{\rm g}$-symmetric one-magnon Raman peak in the magnon Bose-Einstein condensation phase of TlCuCl$_{3}$. Its Raman shift traces the one-magnon energy at the magnetic $\Gamma$ point, and its intensity is proportional to the squared transverse magnetization. The appearance of the one-magnon Raman scattering originates from the exchange magnon Raman process and reflects the change of the magnetic-state symmetry. Using the bond-operator representation, we theoretically clarify the Raman selection rules, being consistent with the experimental results.