Imaging the charge density wave in rare-earth tellurides

Rare-earth tritellurides (RTe₃; R = rare-earth element) are quasi-2D materials showing unidirectional, incommensurate charge density waves (CDWs). The heavier rare-earth elements in RTe₃ can have a second CDW perpendicular to the first one, making it a bidirectional CDW. The CDW state and the transition temperature can be tuned by different rare-earth elements: from La-Tb, a unidirectional CDW is observed, but for Dy-Tm, the CDW is bidirectional. While previous studies suggest an interplay between the two CDWs [1], a proper understanding of the dynamics of the second CDW evolution is still lacking. Moreover, the incommensurate nature of the CDW is unclear [2,3]. In this study, we investigate LaTe₃ with a unidirectional CDW at room temperature and ErTe₃ that transitions to a unidirectional CDW at 265 K and a bidirectional CDW below 155 K. We use atomic-resolution STEM-HAADF imaging, 4D STEM, and electron diffraction to study the effects of nanoscale confinement, nature of the incommensurate lattice modulations, and evolution of the two CDW orders as we vary the temperature from 300 K to 120 K.

[1] A. A. Sinchenko, et al., Phys. Rev. B 93, 235141 (2016).

[2] A. Tomic, et al., Phys. Rev. B 79, 085422 (2009).

[3] A. Fang, et al., Phys. Rev. Lett. 99, 046401 (2007).