skip to main content


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

One of the most fundamental properties of an interacting electron system is its frequency- and wave-vector-dependent density response function, \chi({\bf q},\omega) . The imaginary part, \chi''({\bf q},\omega) , defines the fundamental bosonic charge excitations of the system, exhibiting peaks wherever collective modes are present. \chi χ quantifies the electronic compressibility of a material, its response to external fields, its ability to screen charge, and its tendency to form charge density waves. Unfortunately, there has never been a fully momentum-resolved means to measure \chi({\bf q},\omega) at the meV energy scale relevant to modern electronic materials. Here, we demonstrate a way to measure \chi χ with quantitative momentum resolution by applying alignment techniques from x-ray and neutron scattering to surface high-resolution electron energy-loss spectroscopy (HR-EELS). This approach, which we refer to here as “M-EELS”, allows direct measurement of \chi''({\bf q},\omega) with meV resolution while controlling the momentum with an accuracy better than a percent of a typical Brillouin zone. We apply this technique to finite-q excitations in the optimally-doped high temperature superconductor, Bi _2 2 Sr _2 2 CaCu _2 2 O _{8+x} 8 + x (Bi2212), which exhibits several phonons potentially relevant to dispersion anomalies observed in ARPES and STM experiments. Our study defines a path to studying the long-sought collective charge modes in quantum materials at the meV scale and with full momentum control.
ORCiD logo [1] ; ORCiD logo [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [3] ;  [1] ;  [4]
  1. Univ. of Illinois, Urbana, IL (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357; AC02-98CH10886; SC0012368
Published Article
Journal Name:
SciPost Physics
Additional Journal Information:
Journal Volume: 3; Journal Issue: 4; Journal ID: ISSN 2542-4653
Stichting SciPost
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Energy Frontier Research Center; Center for Emergent Superconductivity; Gordon and Betty Moore Foundation; Alexander von Humboldt Foundation; USDOE
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1418460