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 ¼ 0 (intra–unit-cell) and →Q ≠ 0 (density-wave) broken-symmetry states, simultaneously with the coherent →k ‐space topology, for Bi2Sr2CaCu2O8+d 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 pc = 0.19. Concomitantly, the coherent →k ‐space topology undergoes an abrupt transition, from arcs to closed contours, at the same pc. 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.