Effect of dimensionality on sliding charge density waves: The quasi-two-dimensionalTbTe3system probed by coherent x-ray diffraction

We report on sliding charge density waves (CDWs) in the quasi-two-dimensional ${\mathrm{TbTe}}₃$ system probed by coherent x-ray diffraction combined with in situ transport measurements. We show that the non-Ohmic conductivity in ${\mathrm{TbTe}}₃$ is made possible thanks to a strong distortion of the CDW. Our diffraction experiment versus current shows first that the CDW remains undeformed below the threshold current ${I}_S$ and then suddenly rotates and reorders by motion above threshold. Contrary to quasi-one-dimensional systems, the CDW in ${\mathrm{TbTe}}₃$ does not display any phase shifts below ${I}_S$ and tolerates only slow spatial variations of the phase above. This is the first observation of CDW behavior in the bulk in a quasi-two-dimensional system allowing collective transport of charges at room temperature.