Electronic nematicity in cuprates and ruthenates.

Over the course of extensive experimental studies of La_2-xSr_xCuO₄ films synthesized by molecular beam epitaxy, we discovered that a spontaneous voltage develops across the sample, transverse to the electrical current¹. The sign and magnitude of this transverse voltage oscillates with the in-plane direction of the current as a consequence of the anisotropy in electronic transport. This unusual metallic state, in which the rotational symmetry of the electron fluid is spontaneously broken, is of purely electronic origin, the so-called ‘electronic nematicity’. The director of nematicity does not align with the crystal lattice axes. We observe nematicity in a large temperature and doping region; the superconducting state always emerges out of this nematic metal state¹. Our newest results showing that electronic nematicity also occurs in superconducting ruthenates will also be presented.

¹ J. Wu, A. T. Bollinger, X. He and I. Bozovic, Nature 547, 432 (2017).