Emergence of pseudogap from short-range spin-correlations in electron-doped cuprates

Abstract

Electron interactions are pivotal for defining the electronic structure of quantum materials. In particular, the strong electron Coulomb repulsion is considered the keystone for describing the emergence of exotic and/or ordered phases of quantum matter as disparate as high-temperature superconductivity and charge-or 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 angleresolved photoemission spectroscopy to unveil the temperature evolution of the low-energy density of states in the electron-doped cuprate Nd 2-x Ce x CuO 4 , an emblematic system where the pseudogap intertwines with magnetic degrees of freedom. By photoexciting the electronic system across the pseudogap onset temperature T*, we report the direct relation between the momentum-resolved pseudogap spectral features and the spin-correlation length with an unprecedented 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.

Ubiquitous suppression of the nodal coherent spectral weight in Bi-based cuprates

“…For both compounds, we observe a clear suppression of CSW close to the Fermi energy (E F ), as the temperature increases from 30 to 90 K. As an alternative approach to standard Tdependent ARPES, in this work we employ TR-ARPES to meticulously track the temperature-dependent modifications of the low-energy nodal spectral features by tuning the transient electronic temperature T e via optical pumping. Due to the strong electron interactions underlying the cuprates, quasiparticles excited via near-infrared light thermalize on an ultrashort timescale (i.e., ∼100 fs; note that a similar timescale was reported also for the photodoping effects [22]), entering a state of quasiequilibrium where an effective electronic temperature can be defined at each pumpprobe delay [13,23,24]. This method allows one to directly link the transient electronic temperature to the progression of the ARPES spectral features, effectively performing a T -dependent measurement with minimal repercussions from surface degradation and sample drifting.…”

Time-resolved ARPES on cuprates: Tracking the low-energy electrodynamics in the time domain

“…To date, only two TR-ARPES studies have directly tracked the transient evolution of the pseudogap. This was done at the antiferromagnetic hot spot for the electron-doped cuprate Nd 2-x Ce x CuO 4 [25], and at the antinode in the holedoped bilayer material Bi2212 [43]. In the latter case, the appearance of antinodal in-gap states [see Fig.…”

“…Cuprates are a prototypical example of a strongly correlated system: their phase diagram hosts a multitude of quantum phases whose origin and interplay are still under debate, such as (but not limited to) unconventional superconductivity, Mott insulating behavior, pseudogap phenomenon, charge order, and band-structure renormalization due to electron-boson coupling (the so called kink ) [20][21][22][23][24]. Here we offer a brief overview of the TR-ARPES research on cuprates over the past 15 years, as well as a comprehensive discussion of the transient evolution of the lowenergy one-electron removal spectral function in Bi-based cuprates based on some of our recent works [19,25,26], and new experimental data.…”

Role of matrix elements in the time-resolved photoemission signal

“…While the technique is by now fairly wellestablished, interpretation and analysis of TR-ARPES has yet to take advantage of the vast amount of information encoded in the experimental signal. Presently, it is conventional to emphasize the temporal evolution of the electronic temperature [4,[9][10][11][12] or the photoemission intensity in well-defined momentum-energy regions [13][14][15][16].…”