Nematic superconducting phase fluctuations in a cuprate superconductor

We present angle-resolved transverse magnetoresistance measurements of single crystal thin films of the cuprate superconductor La_2-xSr_xCuO₄, 0.02 ≤ x ≤ 0.25. The strong nematic signal in the normal state transverse resistance close to T_c originally found in [Wu, J., Bollinger, A.T., He, X. and Božović, I., 2017. Nature, 547(7664), pp.432-435] is identified as being due to superconducting fluctuations. By modelling the conductivity due to normal electrons and thermally occupied Cooper pairs (i.e. Aslamazov-Larkin paraconductivity) we find that the pair stiffness is exceptionally anisotropic, quasi one-dimensional, at low doping. We discuss the observations in the context of theories where anisotropic superconductivity is expected such as stripe or pair-density wave order.