Atomic-scale Electronic Structure of the Cuprate d-Symmetry Form Factor Density Wave State

TL;DR

This study reveals that the d-symmetry form factor density wave in cuprates is intimately linked to the pseudogap energy, exhibits a specific phase relationship between filled and empty states, and is connected to scattering in hot frontier regions of momentum space.

Contribution

It provides a detailed microscopic characterization of the dFF-DW state, linking it to the pseudogap energy and specific momentum-space scattering processes.

Findings

dFF-DW energy matches the pseudogap energy Δ₁

dFF-DW modulations at -Δ₁ and Δ₁ are out of phase by π

Q-vector corresponds to scattering between hot frontier regions

Abstract

Extensive research into high temperature superconducting cuprates is now focused upon identifying the relationship between the classic 'pseudogap' phenomenon$^{1,2}$ and the more recently investigated density wave state$^{3-13}$. This state always exhibits wave vector $Q$ parallel to the planar Cu-O-Cu bonds$^{4-13}$ along with a predominantly $d$-symmetry form factor$^{14-17}$ (dFF-DW). Finding its microscopic mechanism has now become a key objective$^{18-30}$ of this field. To accomplish this, one must identify the momentum-space ($k$-space) states contributing to the dFF-DW spectral weight, determine their particle-hole phase relationship about the Fermi energy, establish whether they exhibit a characteristic energy gap, and understand the evolution of all these phenomena throughout the phase diagram. Here we use energy-resolved sublattice visualization$^{14}$ of electronic structure and show that the characteristic energy of the dFF-DW modulations is actually the 'pseudogap' energy $\Delta_{1}$. Moreover, we demonstrate that the dFF-DW modulations at $E=-\Delta_{1}$ (filled states) occur with relative phase $\pi$ compared to those at $E=\Delta_{1}$ (empty states). Finally, we show that the dFF-DW $Q$ corresponds directly to scattering between the 'hot frontier' regions of $k$-space beyond which Bogoliubov quasiparticles cease to exist$^{31,32,33}$. These data demonstrate that the dFF-DW state is consistent with particle-hole interactions focused at the pseudogap energy scale and between the four pairs of 'hot frontier' regions in $k$-space where the pseudogap opens.