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Title: Temperature-Dependent Ellipsometry Measurements of Partial Coulomb Energy in Superconducting Cuprates

Here we performed an experimental study of the temperature and doping dependence of the energy-loss function of the bilayer and trilayer bismuth cuprates family. The primary aim is to obtain information on the energy stored in the Coulomb interaction between the conduction electrons, on the temperature dependence thereof, and on the change of Coulomb interaction when Cooper pairs are formed. We performed temperature-dependent ellipsometry measurements on several Bi2Sr2CaCu2O8₋x single crystals: underdoped with Tc=60, 70, and 83 K; optimally doped with Tc=91 K; overdoped with Tc=84, 81, 70, and 58 K; as well as optimally doped Bi2Sr2Ca2Cu3O10+x with Tc=110 K. Our first observation is that, as the temperature drops through Tc, the loss function in the range up to 2 eV displays a change of temperature dependence as compared to the temperature dependence in the normal state. This effect at—or close to—Tc depends strongly on doping, with a sign change for weak overdoping. The size of the observed change in Coulomb energy, using an extrapolation with reasonable assumptions about its q dependence, is about the same size as the condensation energy that has been measured in these compounds. Our results therefore lend support to the notion that the Coulomb energy ismore » an important factor for stabilizing the superconducting phase. Lastly, because of the restriction to small momentum, our observations do not exclude a possible significant contribution to the condensation energy of the Coulomb energy associated with the region of q around (π,π).« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [1] ;  [1] ;  [4] ;  [5] ;  [1]
  1. Univ. of Geneva (Switzerland). Dept. of Quantum Matter Physics
  2. Univ. of Illinois, Urbana-Champaign, IL (United States). Dept. of Physics
  3. Philips Research, Eindhoven (Netherlands)
  4. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
  5. Univ. of Illinois, Urbana-Champaign, IL (United States). Dept. of Physics; Univ. of Waterloo, ON (Canada). Inst. of Quantum Computing
Publication Date:
Report Number(s):
BNL-113255-2016-JA
Journal ID: ISSN 2160-3308; R&D Project: PO010; KC0201060
Grant/Contract Number:
SC00112704; AC02-07CH11358
Type:
Published Article
Journal Name:
Physical Review. X
Additional Journal Information:
Journal Volume: 6; Journal Issue: 3; Journal ID: ISSN 2160-3308
Publisher:
American Physical Society
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Swiss National Science Foundation (SNSF)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1305439
Alternate Identifier(s):
OSTI ID: 1336224