Signatures of Domain-Wall Confinement in Raman Spectroscopy of Ising Spin Chains

Mesonic bound states of domain walls can be stabilized in quasi one-dimensional magnetic compounds. Here, we theoretically study the Raman light scattering response of a twisted Kitaev chain with tilted magnetic fields as a minimal model for confinement in $\text{CoNb}_{2}\text{O}_{6}$. By both numerical matrix product states and few-domain wall variational states, we show that confinement-induced bound states directly manifest themselves as sharp peaks in the Raman response. Near quantum criticality the Raman spectrum exhibit the famous E$_{8}$ symmetry. Remarkably, by tuning the polarization of the incident light field, we demonstrate that the Raman response offers new insights into the intrinsic structure of the bound state wavefunction.