Commensurate Fluctuations in the Pseudogap and Incommensurate spin-Peierls Phases of TiOCl

TL;DR

This study uses X-ray scattering to investigate TiOCl, revealing persistent commensurate dimerization peaks across different phases, indicating long-range correlations and coexistence of phases over a broad temperature range.

Contribution

It provides new insights into the coexistence and evolution of commensurate and incommensurate phases in TiOCl using detailed scattering measurements.

Findings

Commensurate dimerization peaks are present in both the incommensurate and pseudogap phases.

Correlation lengths exceed 100 Å below T* ~ 130 K.

The scattering features evolve continuously with temperature.

Abstract

X-ray scattering measurements on single crystals of TiOCl reveal the presence of commensurate dimerization peaks within both the incommensurate spin-Peierls phase and the so-called pseudogap phase above T_c2. This scattering is relatively narrow in Q-space indicating long correlation lengths exceeding ~ 100 A below T* ~ 130 K. It is also slightly shifted in Q relative to that of the commensurate long range ordered state at the lowest temperatures, and it coexists with the incommensurate Bragg peaks below T_c2. The integrated scattering over both commensurate and incommensurate positions evolves continuously with decreasing temperature for all temperatures below T* ~ 130 K.