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This content will become publicly available on November 16, 2016

Title: Evidence of superconductivity-induced phonon spectra renormalization in alkali-doped iron selenides

Polarized Raman scattering spectra of superconducting KxFe2-ySe2 and nonsuperconducting K0.8Fe1.8Co0.2Se2 single crystals were measured in a temperature range from 10 K up to 300 K. Two Raman active modes from the I4/mmm phase and seven from the I4/m phase are observed in frequency range from 150 to 325 cm -1 in both compounds, suggesting that K0.8Fe1.8Co0.2Se2 single crystal also has two-phase nature. Temperature dependence of Raman mode energy is analyzed in terms of lattice thermal expansion and phonon-phonon interaction. Temperature dependence of Raman mode linewidth is considered as temperature-induced anharmonic effects. It is shown that change of Raman mode energy with temperature is dominantly driven by thermal expansion of the crystal lattice. Abrupt change of the A1g mode energy near TC was observed in KxFe2-ySe2 , whereas it is absent in K0.8Fe1.8Co0.2Se2. Phonon energy hardening at low temperatures in the superconducting sample is a consequence of superconductivity-induced redistribution of the electronic states below critical temperature.
 [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [2] ;  [1]
  1. Univ. of Belgrade, Belgrade (Serbia). Institute of Physics Belgrade
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.; Stony Brook Univ., NY (United States). Dept. of Physics and Astronomy
  3. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0953-8984; R&D Project: PM016; KC0201050
Grant/Contract Number:
SC00112704; Ac02-98CH10886
Accepted Manuscript
Journal Name:
Journal of Physics. Condensed Matter
Additional Journal Information:
Journal Volume: 27; Journal Issue: 48; Journal ID: ISSN 0953-8984
IOP Publishing
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States