Double Vibronic process in the quantum spin ice candidate Tb${}_2$Ti${}_2$O${}_7$ revealed by terahertz spectroscopy

Abstract

The origin of quantum fluctuations responsible for the spin liquid state in Tb${}_2$Ti${}_2$O${}_7$ has remained a long standing problem. By synchrotron-based terahertz measurements, we show evidence of strong coupling between the magnetic and lattice degrees of freedom that provides a path to the quantum melting process. As revealed by hybrid crystal electric field-phonon excitations that appear at 0.67 THz below 200 K, and around 0.42 THz below 50 K, the double vibronic process is unique for Tb${}^{3+}$ in the titanate family due to adequate energy matching and strong quadrupolar moments. The results suggest that lattice motion can indeed be the driving force behind spin flips within the hybridized ground and first excited states, promoting quantum terms in the effective Hamiltonian that describes Tb${}_2$Ti${}_2$O${}_7$.

References in corpus (4)

• Pyrochlore Photons: The U(1) Spin Liquid in a S=1/2 Three-Dimensional Frustrated Magnet
• Dynamically-Induced Frustration as a Route to a Quantum Spin Ice State in Tb2Ti2O7 via Virtual Crystal Field Excitations and Quantum Many-Body Effects
• Phonon and crystal field excitations in geometrically frustrated rare earth titanates
• Structural distortion and the spin liquid state in Tb2Ti2O7

Cited by in corpus (1)

• Intertwined Magnetic Dipolar and Electric Quadrupolar Correlations in the Pyrochlore Tb${}_2$Ge${}_2$O${}_7$