English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

One of the most fundamental properties of an interacting electron system isits frequency- and wave-vector-dependent density response function, $\chi({\bfq},\omega)$. The imaginary part, $\chi''({\bf q},\omega)$, defines thefundamental bosonic charge excitations of the system, exhibiting peaks wherevercollective modes are present. $\chi$ quantifies the electronic compressibilityof a material, its response to external fields, its ability to screen charge,and its tendency to form charge density waves. Unfortunately, there has neverbeen a fully momentum-resolved means to measure $\chi({\bf q},\omega)$ at themeV energy scale relevant to modern elecronic materials. Here, we demonstrate away to measure $\chi$ with quantitative momentum resolution by applyingalignment techniques from x-ray and neutron scattering to surfacehigh-resolution electron energy-loss spectroscopy (HR-EELS). This approach,which we refer to here as "M-EELS," allows direct measurement of $\chi''({\bfq},\omega)$ with meV resolution while controlling the momentum with an accuracybetter than a percent of a typical Brillouin zone. We apply this technique tofinite-q excitations in the optimally-doped high temperature superconductor,Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ (Bi2212), which exhibits several phononspotentially relevant to dispersion anomalies observed in ARPES and STMexperiments. Our study defines a path to studying the long-sought collectivecharge modes in quantum materials at the meV scale and with full momentumcontrol.

Measurement of the dynamic charge response of materials using low-energy, momentum-resolved electron energy-loss spectroscopy (M-EELS)