In-Plane Anisotropy of Charge Density Wave Fluctuations in 1T-TiSe₂

We report measurements of anisotropic triple-q charge density wave (CDW) fluctuations in the transition metal dichalcogenide 1T-TiSe2 over a large volume of reciprocal space with x-ray diffuse scattering. Above the transition temperature, TCDW, the in-plane diffuse scattering is marked by ellipses which reveal that the in-plane fluctuations are anisotropic. In addition, the out-of-plane diffuse scattering is characterized by rodlike structures which indicate that the CDW fluctuations in neighboring layers are largely decoupled. Our analysis of the diffuse scattering line shapes and orientations suggests that the three charge density wave components contain independent phase fluctuations with a hierarchy of length scales, leading to intricate fluctuation patterns that go beyond the conventional 2D-to-3D crossover picture.