Abstract
Complex electron interactions underlie the electronic structure of several families of quantum materials. In particular, the strong electron Coulomb repulsion is considered the key ingredient to describing the emergence of exotic and/or ordered phases of quantum matter, from high-temperature superconductivity to charge- and magnetic-order. However, a comprehensive understanding of fundamental electronic properties of quantum materials is often complicated by the appearance of an enigmatic partial suppression of low-energy electronic states, known as the pseudogap. Here we take advantage of ultrafast angle-resolved photoemission spectroscopy to unveil the temperature evolution of the low-energy density of states in the electron-doped cuprate Nd2-xCexCuO4, an emblematic system where the pseudogap intertwines with magnetic degrees of freedom. Using an optical excitation we drive the electronic system across the pseudogap onset temperature T*, and we report the direct relation between the momentum-resolved pseudogap spectral features and the spin-correlation length with a remarkable sensitivity. This transient approach, corroborated by mean-field model calculations, allows us to establish the pseudogap in electron-doped cuprates as a precursor to the incipient antiferromagnetic order even when long-range antiferromagnetic correlations are not established, as in the case of optimal doping.
Highlights
Scattering experiments on electron-doped cuprates have shown that the long-range AF order disappears when entering the narrow SC dome,[23,24] and that the commonly reported charge-order in cuprates does not exhibit a clear connection to the AF order,[25,26] a coupling to dynamic magnetic correlations has been recently shown.[27]
For Te = 130 K the shortening of ξspin leads to a filling-up of the PG. f Simulated (f1) and experimental (f2) differential energy distribution curves (EDCs), as defined in Eq (2), where we demonstrate that a filling of the PG manifests as an increase of the photoemission intensity at ω ~ −50 meV
The experimental differential momentum-integrated EDCs (dEDCs) are reproduced through a substantial increase of the broadening term Γ alone, which phenomenologically describes the filling of the PG due to the reduction of the spin-correlation length.[32,48]
Summary
Scattering experiments on electron-doped cuprates have shown that the long-range AF order disappears when entering the narrow SC dome,[23,24] and that the commonly reported charge-order in cuprates does not exhibit a clear connection to the AF order,[25,26] a coupling to dynamic magnetic correlations has been recently shown.[27] In addition, 3D collective charge modes, which may play a substantial role in mediating high-temperature superconductivity, have been reported.[28]. Most importantly, a momentum-resolved study connecting explicitly the PG spectral features and short-range AF correlations in electron-doped cuprates is still missing
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