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 ^→-space) electronic structure underpinning the superconductivity has not yet been established. Here, we visualize the Q^→ = 0 (intra-unit-cell) and Q^→ ≠ 0 (density-wave) broken-symmetry states, simultaneously with the coherent k^→-space topology, for Bi₂Sr₂CaCu₂O_8+δ samples spanning the phase diagram 0.06 ≤ p ≤ 0.23. We show that the electronic symmetry-breaking tendencies weaken with increasing p and disappear close to a critical doping p_c = 0.19. Concomitantly, the coherent k ^→-space topology undergoes an abrupt transition, from arcs to closed contours, at the same p_c. These data reveal that the k ^→-space topology transformation in cuprates is linked intimately with the disappearance of the electronic symmetry breaking at a concealed critical point.