Structural Fluctuations in the Spin Liquid State of Tb2Ti2O7

TL;DR

This study investigates the structural fluctuations in Tb2Ti2O7, revealing finite correlations and anomalies at low temperatures that suggest proximity to a Jahn-Teller phase transition in a spin liquid state.

Contribution

It provides high-resolution X-ray scattering evidence of structural fluctuations and anomalies in Tb2Ti2O7, linking them to potential phase transition behavior in a geometrically frustrated spin liquid.

Findings

Finite structural correlations at low temperatures.

Anomalous lattice expansion below 18 K.

Evidence of fluctuations near a Jahn-Teller transition.

Abstract

High resolution X-ray scattering measurements on single crystal Tb2Ti2O7 reveal finite structural correlations at low temperatures. This geometrically frustrated pyrochlore is known to exhibit a spin liquid, or cooperative paramagnetic state, at temperatures below ~ 20 K. Parametric studies of structural Bragg peaks appropriate to the Fd$\bar{3}$m space group of Tb2Ti2O7 reveal substantial broadening and peak intensity reduction in the temperature regime 20 K to 300 mK. We also observe a small, anomalous lattice expansion on cooling below a density maximum at ~ 18 K. These measurements are consistent with the development of fluctuations above a cooperative Jahn-Teller, cubic-tetragonal phase transition at very low temperatures.