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

Abstract

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 $\chi$ 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 $\chi$ 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.

Authors:

Vig, Sean ^[1]; Kogar, Anshul ^[1]; Mitrano, Matteo  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-0102-0391"

Husain, Ali  ^[1];

• Search DOE PAGES for author "Husain, Ali"
• Search DOE PAGES for ORCID "0000-0001-9865-9476"

Venema, Luc ^[1]; Rak, Mindy ^[1]; Mishra, Vivek ^[2]; Johnson, Peter ^[3]; Gu, Genda ^[3]; Fradkin, Eduardo ^[1]; Norman, Michael ^[4]; Abbamonte, Peter ^[1]

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+ Show Author Affiliations

1. University of Illinois at Urbana Champaign
2. Oak Ridge National Laboratory
3. Brookhaven National Laboratory
4. Argonne National Laboratory

Publication Date:

Fri Oct 06 00:00:00 EDT 2017

Research Org.:

Argonne National Lab. (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE; USDOE Office of Science (SC), Energy Frontier Research Center; Center for Emergent Superconductivity; Gordon and Betty Moore Foundation; Alexander von Humboldt Foundation

OSTI Identifier:

1398288

Alternate Identifier(s):

OSTI ID: 1418460

Grant/Contract Number:  

AC02-98CH10886; SC0012368; AC02-06CH11357

Resource Type:

Published Article

Journal Name:

SciPost Physics Proceedings

Additional Journal Information:

Journal Name: SciPost Physics Proceedings Journal Volume: 3 Journal Issue: 4; Journal ID: ISSN 2542-4653

Publisher:

Stichting SciPost

Country of Publication:

Netherlands

Language:

English

Subject:

36 MATERIALS SCIENCE