Ultrafast measurements under anisotropic strain reveal near equivalence of competing charge orders in TbTe_3

We report ultrafast reflectivity measurements of the dynamics of the order parameter of the charge density wave (CDW) in TbTe_3 under anisotropic strain. We observe an increase in the frequency of the amplitude mode with increasing tensile strain along the a-axis (which drives the lattice into a>c, with a and c the lattice constants), and similar behavior for tensile strain along c (c>a). This suggests that both strains stabilize the corresponding CDW order and further support the near equivalence of the CDW phases oriented in a- and c-axis, in spite of the orthorhombic space group. The results were analyzed within the time-dependent Ginzburg-Landau framework, which agrees well with the reflectivity dynamics.