Nematicity in stripe ordered cuprates probed via resonant x-ray   scattering
  In underdoped cuprate superconductors, a rich competition occurs between superconductivity and charge density wave (CDW) order. Whether rotational symmetry breaking (nematicity) occurs intrinsically and generically or as a consequence of other orders is under debate. Here we employ resonant x-ray scattering in stripe-ordered (La,M)_2CuO_4 to probe the relationship between electronic nematicity of the Cu 3d orbitals, structure of the (La,M)_2O_2 layers, and CDW order. We find distinct temperature dependences for the structure of the (La,M)_2O_2 layers and the electronic nematicity of the CuO_2 planes, with only the latter being enhanced by the onset of CDW order. These results identify electronic nematicity as an order parameter that is distinct from a purely structural order parameter in underdoped striped cuprates. 
A. J. Achkar, M. Zwiebler, Christopher McMahon, F. He, R. Sutarto,   Isaiah Djianto, Zhihao Hao, M. J. P. Gingras, M. H\"uck...
cond-mat.supr-con cond-mat.str-el