Physical review. B./Physical review. B
Optical selection rules of the magnetic excitation in the S=12 one-dimensional Ising-like antiferromagnet BaCo2V2O8
Shojiro Kimura, Hiroaki Onishi, Akira Okutani, Mitsuru Akaki, Yasuo Narumi, Masayuki Hagiwara, Kouichi Okunishi, Koichi Kindo, Zhangzhen He, Tomoyasu Taniyama, Mitsuru Itoh
Abstract
In this study, we clarify the selection rules of optical transitions from the ground state to the magnetic excited states in the quasi-one-dimensional quantum Ising-like antiferromagnet ${\mathrm{BaCo}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$ with spin $S=\frac{1}{2}$ using the high-field electron spin resonance measurement with illuminating polarized electromagnetic waves. We demonstrate that the unconventional magnetic excitation via the pair creation of quasipaticles at wave numbers ${q}_{z}$ = $\ensuremath{\pi}/2$ and $\ensuremath{\pi}$ in the field-induced quantum critical state can couple with both oscillating magnetic and electric fields. Our density matrix renormalization group calculations indicate that the observed selection rules can be explained by two- and four-fold periodical spin interactions, originating from the screw chain structure in ${\mathrm{BaCo}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$, in addition to the magnetoelectric coupling between spins and electric dipoles.