skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Giant two-phonon Raman scattering from nanoscale NbC precipitates in Nb

; ; ; ; ; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
OSTI Identifier:
Grant/Contract Number:
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 91; Journal Issue: 9; Journal ID: ISSN 1098-0121
American Physical Society
Country of Publication:
United States

Citation Formats

Cao, C., Tao, R., Ford, D. C., Klie, R. F., Proslier, T., Cooley, L. D., Dzyuba, A., Zapol, P., Warren, M., Lind, H., and Zasadzinski, J. F.. Giant two-phonon Raman scattering from nanoscale NbC precipitates in Nb. United States: N. p., 2015. Web. doi:10.1103/PhysRevB.91.094302.
Cao, C., Tao, R., Ford, D. C., Klie, R. F., Proslier, T., Cooley, L. D., Dzyuba, A., Zapol, P., Warren, M., Lind, H., & Zasadzinski, J. F.. Giant two-phonon Raman scattering from nanoscale NbC precipitates in Nb. United States. doi:10.1103/PhysRevB.91.094302.
Cao, C., Tao, R., Ford, D. C., Klie, R. F., Proslier, T., Cooley, L. D., Dzyuba, A., Zapol, P., Warren, M., Lind, H., and Zasadzinski, J. F.. 2015. "Giant two-phonon Raman scattering from nanoscale NbC precipitates in Nb". United States. doi:10.1103/PhysRevB.91.094302.
title = {Giant two-phonon Raman scattering from nanoscale NbC precipitates in Nb},
author = {Cao, C. and Tao, R. and Ford, D. C. and Klie, R. F. and Proslier, T. and Cooley, L. D. and Dzyuba, A. and Zapol, P. and Warren, M. and Lind, H. and Zasadzinski, J. F.},
abstractNote = {},
doi = {10.1103/PhysRevB.91.094302},
journal = {Physical Review B},
number = 9,
volume = 91,
place = {United States},
year = 2015,
month = 3

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevB.91.094302

Citation Metrics:
Cited by: 4works
Citation information provided by
Web of Science

Save / Share:
  • High-purity niobium (Nb), subjected to the processing methods used in the fabrication of superconducting rf cavities, displays micrometer-sized surface patches containing excess carbon. High-resolution transmission electron microscopy and electron energy-loss spectroscopy measurements are presented which reveal the presence of nanoscale NbC coherent precipitates in such regions. Raman backscatter spectroscopy on similar surface regions exhibit spectra consistent with the literature results on bulk NbC but with significantly enhanced two-phonon scattering. The unprecedented strength and sharpness of the two-phonon signal has prompted a theoretical analysis, using density functional theory (DFT), of phonon modes in NbC for two different interface models of themore » coherent precipitate. One model leads to overall compressive strain and a comparison to ab initio calculations of phonon dispersion curves under uniform compression of the NbC shows that the measured two-phonon peaks are linked directly to phonon anomalies arising from strong electron-phonon interaction. Another model of the extended interface between Nb and NbC, studied by DFT, gives insight into the frequency shifts of the acoustic and optical mode density of states measured by first-order Raman spectroscopy. The exact origin of the stronger two-phonon response is not known at present but it suggests the possibility of enhanced electron-phonon coupling in transition-metal carbides under strain found either in the bulk NbC inclusions or at their interfaces with Nb metal. Preliminary tunneling studies using a point contact method show some energy gaps larger than expected for bulk NbC.« less
  • Raman scattering in CeAl/sub 2/ probes the interacting phonon (anti Gamma/sub 6/) and crystalline-electric-field-split anti Gamma/sub 7/-anti Gamma/sub 8/ excitations. The observed 109-cm/sup -1/ Raman peak due to anti Gamma/sub 6/ and the 71-cm/sup -1/ peak (at 5 K) due to anti Gamma/sub 7/ ..-->.. anti Gamma/sub 8(2)/ are in very good agreement with the recent theoretical bound-state model for CeAl/sub 2/. 4 references, 3 figures.
  • We report the temperature dependence of the frequencies of two high-frequency intramolecular modes in {kappa}-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br measured by resonant Raman scattering, with the use of a Fourier-transform spectrometer equipped with an infrared laser. One of these modes, that at 892cm{sup {minus}1} and assigned to {nu}{sub 60}(B{sub 3g}) exhibits an increase below T{sub c} of 2.2{plus_minus}0.7cm{sup {minus}1} and 2.2{plus_minus}0.4cm{sup {minus}1} when measured in a Janis Dewar and in a Heli-Tran refrigerator, respectively. A smaller increase is observed in the deuterated sample and no increase is observed at all if the samples are cooled too rapidly. Two other modes, {nu}{sub 3}(A{submore » g}) at 1474cm{sup {minus}1} and {nu}{sub 9}(A{sub g}) at 503cm{sup {minus}1}, show no such increase below T{sub c} in the slowly cooled samples. We speculate that the normal electron-phonon interaction may not be responsible for the frequency increase but that the superconducting transition may involve a change in either the geometry or the arrangement of the BEDT-TTF molecules to which the particular mode is sensitive. {copyright} {ital 1998} {ital The American Physical Society}« less
  • The probability of Raman scattering of light by a charge-density-wave (CDW) phonon is calculated for a model anisotropic system which exhibits coexistent CDW and superconducting characteristics. It is pointed out that in such a system both ordinary electron-phonon interactions and the modified Balseiro-Falicov interaction contribute to the Raman activity of the CDW phonon. The Raman spectrum obtained has features qualitatively similar to that of the renormalized spectral function of the CDW phonon previously discussed. However, the inclusion of the electron-photon vertices may considerably enhance the weight of the superconducting gap peak relative to the CDW amplitude mode. The polarizations ofmore » the incident and scattered light enter the expressions of the scattering probability, thus giving a natural explanation for the intensity difference of the gap peaks in the A and E modes observed in experiments by Sooryakumar and Klein on 2H-NbSe/sub 2/.« less
  • Micro-Raman scattering and its temperature dependencies have been used to investigate lattice dynamic properties of {beta}-FeSi{sub 2} thin films epitaxially grown on Si (111) substrates by sputtering at elevated temperatures. A linear correlation between the blueshift in phonon energies and the lattice expansions in the growth direction of {beta}-FeSi{sub 2} is observed. The shifting rate of the Raman mode at 248 cm{sup -1} (13.6 cm{sup -1}/%) is much larger than that of the mode at 194 cm{sup -1} (8.4 cm{sup -1}/%) due to the involvement of radial bonding vibrations between Fe and Si atoms. Temperature-dependent Raman scattering, which is hithertomore » unknown for {beta}-FeSi{sub 2}, reveals an extremely small phonon line width broadening in the range of 80-480 K. It is revealed that the broadening in the phonon line widths contributed by phonon-phonon scattering is weaker and is masked by phonon-hole couplings in {beta}-FeSi{sub 2}, while the effect of phonon-hole coupling on phonon line width broadening is saturated at the studied temperatures due to the high impurity densities.« less