Crystal-field excitations and vibronic modes in the triangular-lattice spin-liquid candidate TbInO3

We study the ground-state properties, the electronic excitations, and lattice dynamics in spin-liquid candidate TbInO3. By employing polarization-resolved Raman spectroscopy we define the intermultiplet and intramultiplet excitations, and establish the low-energy crystal-field (CF) level scheme. In particular, we demonstrate that the ground state of the Tb3+ ions is a non-Kramers doublet, and relate the enhanced linewidth of the CF modes to the magnetic fluctuations near the spin-liquid ground state. We identify the 38 allowed Raman-active phonon modes at low temperature. Moreover, we observe hybrid vibronic excitations involving coupled CF and low-lying phonon modes, suggesting strong spin-lattice dynamics. We develop a model for vibronic states and obtain the parameters of the bare responses and coupling strength. We further demonstrate that the obtained CF level scheme is consistent with specific-heat data.

Automated summary

In this study, we investigate the ground-state properties, electronic excitations, and lattice dynamics in the spin-liquid candidate TbInO3 using polarization-resolved Raman spectroscopy. We identify the ground state of Tb3+ ions as a non-Kramers doublet and establish the low-energy crystal-field level scheme. The enhanced linewidth of crystal-field modes is linked to magnetic fluctuations near the spin-liquid ground state, and specific-heat data supports the obtained crystal-field level scheme.