Low Energy Magneto-optics of Tb$_{2}$Ti$_{2}$O$_{7}$ in [111] Magnetic Field

TL;DR

This study uses THz spectroscopy to explore how low energy excitations in Tb$_{2}$Ti$_{2}$O$_{7}$ change under a [111] magnetic field, revealing field-dependent hybridization rather than phase transitions, and highlighting strong spin-lattice coupling.

Contribution

It demonstrates that the low energy spectrum of Tb$_{2}$Ti$_{2}$O$_{7}$ can be explained by field-dependent hybridization and symmetry reduction, emphasizing spin-lattice interactions.

Findings

Low energy excitations shift anomalously with magnetic field.

Spectrum explained by hybridization, not phase transitions.

Strong spin-lattice coupling evidenced by tunable crystal field environment.

Abstract

The pyrochlore magnet Tb$_{2}$Ti$_{2}$O$_{7}$ shows a lack of magnetic order to low temperatures and is considered to be a quantum spin liquid candidate. We perform time-domain THz spectroscopy on high quality Tb$_{2}$Ti$_{2}$O$_{7}$ crystal and study the low energy excitations as a function of [111] magnetic field with high energy resolution. The low energy crystal field excitations change their energies anomalously under magnetic field. Despite several sharp field dependent changes, we show that the material's spectrum can be described not by a phase transitions, but by field dependent hybridization between the low energy crystal field levels. We highlight the strong coupling between spin and lattice degrees of freedom in Tb$_{2}$Ti$_{2}$O$_{7}$ as evidenced by the magnetic field tunable crystal field environment. Calculations based on single ion physics with field induced symmetry reduction of the crystal field environment can reproduce our data.