Visualizing the emergence of the pseudogap state and the evolution to superconductivity in a lightly hole-doped Mott insulator

Abstract

Superconductivity emerges from the cuprate antiferromagnetic Mott state with hole doping. The resulting electronic structure is not understood, although changes in the state of oxygen atoms appear paramount. Hole doping first destroys the Mott state yielding a weak insulator where electrons localize only at low temperatures without a full energy gap. At higher doping, the 'pseudogap', a weakly conducting state with an anisotropic energy gap and intra-unit-cell breaking of 90\degree-rotational (C4v) symmetry appears. However, a direct visualization of the emergence of these phenomena with increasing hole density has never been achieved. Here we report atomic-scale imaging of electronic structure evolution from the weak-insulator through the emergence of the pseudogap to the superconducting state in Ca2-xNaxCuO2Cl2. The spectral signature of the pseudogap emerges at lowest doping from a weakly insulating but C4v-symmetric matrix exhibiting a distinct spectral shape. At slightly higher hole-density, nanoscale regions exhibiting pseudogap spectra and 180\degree-rotational (C2v) symmetry form unidirectional clusters within the C4v-symmetric matrix. Thus, hole-doping proceeds by the appearance of nanoscale clusters of localized holes within which the broken-symmetry pseudogap state is stabilized. A fundamentally two-component electronic structure11 then exists in Ca2-xNaxCuO2Cl2 until the C2v-symmetric clusters touch at higher doping, and the long-range superconductivity appears.

See the Nature Physics website for the published version available at http://dx.doi.org/10.1038/Nphys2321

References in corpus (4)

• An Intrinsic Bond-Centered Electronic Glass with Unidirectional Domains in Underdoped Cuprates
• Two Gaps Make a High Temperature Superconductor?
• How Cooper pairs vanish approaching the Mott insulator in Bi2Sr2CaCu2O8+d
• Evolution of the electronic excitation spectrum with strongly diminishing hole-density in superconducting Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}

Cited by in corpus (4)

• Crossover between BCS Superconductor and Doped Mott Insulator of d-wave Pairing State in Two-Dimensional Hubbard Model
• Strong similarities between the local electronic structure of insulating iron pnictide and lightly doped cuprate
• Angular Dependent Spectral-Weight Transfer and Evidence for Symmetry Broken In-Plane Charge Response in Ca${}_{1.9}$Na${}_{0.1}$CuO${}_2$Cl${}_2$
• Application of Non-local Quantum Hydrodynamics to the Description of the Charged Density Waves in the Graphen Crystal Lattice