Orbital-selective time-domain signature of nematicity dynamics in the charge-density-wave phase of La${}_{1.65}$Eu${}_{0.2}$Sr${}_{0.15}$CuO${}_4$

Abstract

Understanding the interplay between charge, nematic, and structural ordering tendencies in cuprate superconductors is critical to unraveling their complex phase diagram. Using pump-probe time-resolved resonant x-ray scattering on the (0 0 1) Bragg peak at the Cu $L_3$ and O $K$ resonances, we investigate non-equilibrium dynamics of $Q_a=Q_b=0$ nematic order and its association with both charge density wave (CDW) order and lattice dynamics in La${}_{1.65}$Eu${}_{0.2}$Sr${}_{0.15}$CuO${}_4$. The orbital selectivity of the resonant x-ray scattering cross-section allows nematicity dynamics associated with the planar O 2$p$ and Cu 3$d$ states to be distinguished from the response of anisotropic lattice distortions. A direct time-domain comparison of CDW translational-symmetry breaking and nematic rotational-symmetry breaking reveals that these broken symmetries remain closely linked in the photoexcited state, consistent with the stability of CDW topological defects in the investigated pump fluence regime.

19 pages, 5 figures