In-plane anisotropy of charge density wave fluctuations in 1$T$-TiSe$_2$
Xuefei Guo, Anshul Kogar, Jans Henke, Felix Flicker, Fernando de Juan, Stella X. -L. Sun, Issam Khayr, Yingying Peng, Sangjun Lee, Matthew J. Krogstad, Stephan Rosenkranz, Raymond Osborn, Jacob P. C. Ruff, David B. Lioi, Goran Karapetrov, Daniel J. Campbell, Johnpierre Paglione, Jasper van Wezel, Tai C. Chiang, Peter Abbamonte
Published: 2025/1/17
Abstract
We report measurements of anisotropic triple-$q$ charge density wave (CDW) fluctuations in the transition metal dichalcogenide 1$T$-TiSe$_2$ over a large volume of reciprocal space with X-ray diffuse scattering. Above the transition temperature, $T_{\text{CDW}}$, the out-of-plane diffuse scattering is characterized by rod-like structures which indicate that the CDW fluctuations in neighboring layers are largely decoupled. In addition, the in-plane diffuse scattering is marked by ellipses which reveal that the in-plane fluctuations are anisotropic. Our analysis of the diffuse scattering line shapes and orientations suggests that the three charge density wave components contain independent phase fluctuations. At $T_{\text{CDW}}$, long range coherence is established in both the in-plane and out-of-plane directions, consistent with the large observed value of the CDW gap compared to $T_{\text{CDW}}$, and the predicted presence of a hierarchy of energy scales.