Thermodynamic evidence for a nematic phase transition at the onset of the pseudogap in YBa2Cu3Oy

By Y. Sato, S. Kasahara, H. Murayama, Y. Kasahara, E. Moon, T. Nishizaki, T. Loew, J. Porras, Bernhard Keimer, T. Shibauchi and 1 more. Nature Physics, 2017

216 citations recorded by the source corpus.

The pseudogap is an elusive state that is believed to play an important role in the mechanism for high-temperature superconductivity. A torque-magnetometry study of YBCO reveals that its onset is associated with a second-order nematic transition. A long-standing controversial issue in the quest to understand the superconductivity in cuprates is the nature of the enigmatic pseudogap region of the phase diagram1. Especially important is whether the pseudogap state is a distinct thermodynamic phase characterized by broken symmetries below the onset temperature T∗. Here we report torque-magnetometry measurements of anisotropic susceptibility within the ab planes in orthorhombic YBa2Cu3Oy with exceptionally high precision. The in-plane anisotropy displays a significant increase with a distinct kink at the pseudogap onset temperature T∗, showing a remarkable scaling behaviour with respect to T/T∗ in a wide doping range. Our systematic analysis reveals that the rotational symmetry breaking sets in at T∗ in the limit where the effect of orthorhombicity is eliminated. These results provide thermodynamic evidence that the pseudogap onset is associated with a second-order nematic phase transition, which differs from the recently reported charge-density-wave transition that accompanies translational symmetry breaking2,3,4,5,6,7,8,9,10.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics

View Paper: https://www.semanticscholar.org/paper/e3d002ca4f565693d2bac9d91e31cb943dbdff3e