Simultaneous transitions in cuprate momentum-space topology and electronic symmetry breaking
The existence of electronic symmetry breaking in the underdoped cuprates and its disappearance with increased hole density p are now widely reported. However, the relation between this transition and the momentum-space (k â†’-space) electronic structure underpinning the superconductivity has not yet been established. Here, we visualize the Qâ†’ = 0 (intra-unit-cell) and Qâ†’ â‰ 0 (density-wave) broken-symmetry states, simultaneously with the coherent kâ†’-space topology, for Bi2Sr2CaCu2O8+Î´ samples spanning the phase diagram 0.06 â‰¤ p â‰¤ 0.23. We show that the electronic symmetry-breaking tendencies weaken with increasing p and disappear close to a critical doping pc = 0.19. Concomitantly, the coherent k â†’-space topology undergoes an abrupt transition, from arcs to closed contours, at the same pc. These data reveal that the k â†’-space topology transformation in cuprates is linked intimately with the disappearance of the electronic symmetry breaking at a concealed critical point.