The significance of spin-lattice coupling in the phase diagram of the quantum spin-icepyrochlore Tb2Ti2O7 has been a topic of debate for some time. Here, we focus on the aspect of vibronic coupling, which occurs between the Tb3+ electronic levels and transverse acoustic phonons, by studying their dependence on a magnetic field applied along the cubic h111i direction. Our experimental THz spectroscopy measurements, combined with quantitative theoretical quantum calculations, show that indeed vibronic effects are observed at 3 K. An analysis incorporating quadrupolar spin-lattice effects in the Hamiltonian is therefore relevant in this compound, which is no longer optically isotropic but magnetically birefringent.
@article{arxiv.2009.10545,
title = {Terahertz Magneto-optical investigation of quadrupolar spin-lattice effects in magnetically frustrated Tb2Ti2O7},
author = {K. Amelin and Y. Alexanian and U. Nagel and T. Room and J. Robert and J. Debray and V. Simonet and C. Decorse and Z. Wang and R. Ballou and E. Constable and S. de Brion},
journal= {arXiv preprint arXiv:2009.10545},
year = {2026}
}