Terahertz Magneto-optical investigation of quadrupolar spin-lattice effects in magnetically frustrated Tb2Ti2O7

TL;DR

This study uses terahertz spectroscopy and quantum calculations to reveal vibronic and quadrupolar spin-lattice effects in Tb2Ti2O7, highlighting their role in its magnetic birefringence and complex phase behavior.

Contribution

It provides the first experimental and theoretical evidence of vibronic coupling and quadrupolar effects in Tb2Ti2O7, emphasizing their importance in its magnetic properties.

Findings

Vibronic effects observed at 3 K in Tb2Ti2O7.

Quadrupolar spin-lattice effects influence magnetic birefringence.

Experimental data aligns with quantum theoretical models.

Abstract

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.