Nematic Cooper-pair mass renormalization in copper oxide superconductors

We show that the observation of rotational symmetry breaking from transverse resistivity measurements in the normal state of LaSrCuO by Wu et al¹. can be accounted for by the thermal fluctuations of a 2D superconductor with significant in-plane phase stiffness anisotropy. The conductivity tensor is modeled by distinct normal state and paraconducting components, with different effective mass tensors corresponding in general to non-aligned nematic directors and different mass anisotropies. The model is supported by new experimental data showing the rotation of the measured nematic director in the presence of a magnetic field that suppresses superconductivity. The pair mass/phase stiffness anisotropy grows dramatically with underdoping, pointing to an exotic pseudogap state with quasi-one-dimensional pair fluctuations, despite a relatively weak single-particle anisotropy.

1. Wu, J., Bollinger, A., He, X. & Bozović, I. Spontaneous breaking of rotational symmetry in copper oxide superconductors. Nature 547, 432 (2017).