Parity Broken Chiral Spin Dynamics in Ba$_3$NbFe$_3$Si$_2$O$_{14}$

TL;DR

This study investigates chiral spin wave excitations in a langasite crystal, revealing intrinsic chirality in spin dynamics through neutron scattering, without macroscopic time reversal symmetry breaking.

Contribution

It provides the first detailed experimental evidence of intrinsic chiral spin wave excitations in a structurally chiral magnetic material.

Findings

Spectral weight asymmetries linked to structural chirality

Full chirality of spin correlations across energy spectrum

Chiral nature of spin waves without macroscopic time reversal symmetry breaking

Abstract

The spin wave excitations emerging from the chiral helically modulated 120$^{\circ}$ magnetic order in a langasite Ba$_3$NbFe$_3$Si$_2$O$_{14}$ enantiopure crystal were investigated by unpolarized and polarized inelastic neutron scattering. A dynamical fingerprint of the chiral ground state is obtained, singularized by (i) spectral weight asymmetries answerable to the structural chirality and (ii) a full chirality of the spin correlations observed over the whole energy spectrum. The intrinsic chiral nature of the spin waves elementary excitations is shown in absence of macroscopic time reversal symmetry breaking.