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Title: Superconducting energy gap of 2H-NbSe2 in phonon spectroscopy

We present a high-energy-resolution inelastic x-ray scattering data investigation of the charge-density-wave (CDW) soft phonon mode upon entering the superconducting state in 2H–NbSe2. Measurements were done close to the CDW ordering wave vector qCDW at q=qCDW + (0,0,l), 0.15 ≤ l ≤ 0.5, for T = 10K (CDW order) and 3.8K (CDW order+superconductivity). We observe changes of the phonon line shape that are characteristic for systems with strong electron-phonon coupling in the presence of a superconducting energy gap 2Δc and from which we can demonstrate an l dependence of the superconducting gap. Reversely, our data imply that the CDW energy gap is strongly localized along the c* direction. The confinement of the CDW gap to a very small momentum region explains the rather low competition and easy coexistence of CDW order and superconductivity in 2H–NbSe2. Furthermore, the energy gained by opening ΔCDW seems to be too small to be the driving force of the phase transition at TCDW = 33K, which is better described as an electron-phonon coupling driven structural phase transition.
Authors:
 [1] ;  [2] ;  [1] ;  [2]
  1. Karlsruhe Institute of Technology, Karlsruhe (Germany)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
OSTI Identifier:
1352563
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 14; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Argonne National Laboratory (ANL)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Materials Sciences and Engineering Division; Helmholtz Association
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY