The electronic Raman scattering has been investigated in optimally oxygen
doped YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ single crystals as well as in crystals
with non-magnetic, Zn, and magnetic, Ni, impurities. We found that the
intensity of the A$_{1g}$ peak is impurity independent and their energy to
$T_{c}$ ratio is almost constant ($2\Delta/k_{B}T_{c}\sim5$). Moreover, the
signal at the B$_{1g}$ channel is completely smeared out when non-magnetic Zn
impurities are present. These results are qualitatively interpreted in terms of
the Zeyher and Greco's theory that relates the electronic Raman scattering in
the A$_{1g}$ and B$_{1g}$ channels to \textit{d}-CDW and superconducting order
parameters fluctuations, respectively.Comment: Submited to Phys. Rev. Let

A. A. Martin

A. Boch

A. Fournel

A.A. Martin

C. Castellani

C. Rettori

C. T. Lin

C.T. Lin

E. Cappelluti

F. Venturini

H. Martinho

H.F. Fong

H.J. Schulz

I.S. Yang

J. Geerk

J.M. Tranquada

J.W. Quilty

M. Cardona

M. Gurvitch

M. Krantz

M.U. Ubbens

P.A. Lee

R. Zeyher

Raju P. Gupta

S.B. Dierker

Sudip Chakravarty

T. Moriya

T. Strohm

T.P. Devereaux

V. Barzykin

W. Anderson

Y. Gallais

Y. Sidis

English

arXiv

The electronic Raman scattering was investigated in optimally oxygen-doped YBa2Cu3O7-delta single crystals as well in crystals doped with nonmagnetic, Zn2+ and magnetic Ni2+ impurities. We found that the intensity of the A(1g) peak is impurity independent and its energy to T-c ratio is nearly constant (2Delta/k(B)T(c)similar to5). Moreover, the signal at the B-1g channel is completely smeared out when nonmagnetic Zn2+ impurities are present. These results are discussed in terms of the current models of Devereaux , Venturini , and Zeyher and Greco.691

Martinho, H

Martin, AA

Rettori, C

Lin, CT

Repositorio da Producao Cientifica e Intelectual da Unicamp

Origin of the A(1g) and B-1g electronic Raman scattering peaks in the superconducting state of YBa2Cu3O7-delta

The electronic Raman scattering was investigated in optimally oxygen-doped YBa2CU3O7-δ single crystals as well in crystals doped with nonmagnetic, Zn2+ and magnetic Ni2+ impurities. We found that the intensity of the A1g peak is impurity independent and its energy to Tc ratio is nearly constant (2Δ/kBTc∼5). Moreover, the signal at the B 1g channel is completely smeared out when nonmagnetic Zn2+ impurities are present. These results are discussed in terms of the current models of Devereaux et al., Venturini et al., and Zeyher and Greco.69181805011-180501-4Moriya, T., Ueda, K., (2000) Adv. Phys., 49, p. 555Chubukov, A., Pinnes, D., Schmalian, J., (2003) The Physics of Superconductors, , edited by K. H. Bennermann and J. B. Ketterson (Springer-Verlag, Berlin)Barzykin, V., Pines, D., (1995) Phys. Rev. B, 52, pp. 13 585Anderson, W., (1987) Science, 235, p. 1196Ubbens, M.U., Lee, P.A., (1992) Phys. Rev. B, 46, p. 8434Lee, P.A., Wen, X.G., (1997) Phys. Rev. Lett., 78, p. 4111Tranquada, J.M., (1997) Phys. Rev. Lett., 78, p. 338Castellani, C., Di Castro, C., Grilli, M., (1997) Z. Phys. B, 103, p. 137Dierker, S.B., Klein, M.V., Webb, G.W., Fisk, Z., (1983) Phys. Rev. Lett., 50, p. 853Cardona, M., (1999) Physica C, 317, p. 30Yang, I.S., Klein, M.V., Cooper, S.L., Canfield, P.C., Cho, B.K., Lee, S.I., (2000) Phys. Rev. B, 62, p. 1291Quilty, J.W., Lee, S., Yamamoto, A., Tajima, S., (2002) Phys. Rev. Lett., 88, p. 087001Martin, A.A., Hadjiev, V.G., Bernhard, C., Ruf, T., Cardona, M., Wolf, T., (1999) Phys. Status Solidi B, 214, pp. R21Devereaux, T.P., Einzel, D., (1995) Phys. Rev. B, 51, pp. 16 336Devereaux, T.P., (1996) Phys. Rev. B, 54, pp. 12 523Strohm, T., Cardona, M., (1997) Solid State Commun., 9, p. 233Krantz, M., Cardona, M., (1995) J. Low Temp. Phys., 99, p. 205Sidis, Y., Bourges, P., Fong, H.F., Keimer, B., Regnault, L.P., Bossy, J., Ivanov, A., Aksay, I.A., (2000) Phys. Rev. Lett., 84, p. 5900Fong, H.F., Bourges, P., Sidis, Y., Regnault, L.P., Bossy, J., Ivanov, A., Milius, D.L., Keimer, B., (1999) Phys. Rev. Lett., 82, p. 1939Lin, C.T., Li, S.X., Mackenzie, A., Zhou, W., Hunneyball, P.D., Liang, W.Y., (1992) Physica C, 193, p. 129Boch, A., (1999) Ann. Der Phys., 8, p. 441(1999) Phys. Rev. B, 60, p. 3532Strohm, T., Cardona, M., (1997) Phys. Rev. B, 55, pp. 12 725Strohm, T., Hunzar, D., Cardona, M., (1998) Phys. Rev. B, 58, p. 8839Gallais, Y., Sacuto, A., Bourges, P., Sidis, Y., Forget, A., Colson, D., (2002) Phys. Rev. Lett., 88, p. 177401Geerk, J., Xi, X.X., Linker, G., (1988) Z. Phys. B, 73, p. 329Gurvitch, M., Valles, J.M., Cucolo, A.M., Dynes, R.C., Garno, J.P., Schneemeyer, L.F., Wasczak, J.V., (1989) Phys. Rev. Lett., 63, p. 1008Fournel, A., Oujia, I., Sorbier, I., (1988) Europhys. Lett., 6, p. 653Venturini, F., Michelucci, U., Devereaux, T.P., Kampf, A.P., (2000) Phys. Rev. B, 62, pp. 15 204Zeyher, R., Greco, A., (2002) Phys. Rev. Lett., 89, p. 177004Cappelluti, E., Zeyher, R., (1999) Phys. Rev. B, 59, p. 6475Schulz, H.J., (1989) Phys. Rev. B, 39, p. 2940Chakravarty, S., Laughlin, R.B., Morr, D.K., Nayak, C., (2001) Phys. Rev. B, 63, p. 094503Cappelluti, E., Zeyher, R., (2000) Europhys. Lett., 49, p. 487Gupta, R.P., Gupta, M., (1999) Phys. Rev. B, 59, p. 338

Martinho H.

Martin A.A.

Rettori C.

Lin C.T.

RAPID COMMUNICATIONS
PHYSICAL REVIEW B 69, 180501~R! ~2004!Origin of the A1g and B1g electronic Raman scattering peaks in the superconducting state of
YBa2Cu3O7Àd
H. Martinho,1 A. A. Martin,2 C. Rettori,1 and C. T. Lin3
1Instituto de Fı´sica ‘‘Gleb Wataghin,’’ UNICAMP, 13083-970 Campinas, Sa˜o Paulo, Brazil
2Instituto de Pesquisa e Desenvolvimento-UNIVAP, 12244-050 Sa˜o Jose´ dos Campos, Sa˜o Paulo, Brazil
3Max-Planck-Institut fu¨r Festko¨rperforschung, Heisenbergstrasse 1, D-70 569 Stuttgart, Germany
~Received 23 February 2004; published 4 May 2004!
The electronic Raman scattering was investigated in optimally oxygen-doped YBa2Cu3O72d single crystals
as well in crystals doped with nonmagnetic, Zn21 and magnetic Ni21 impurities. We found that the intensity
of the A1g peak is impurity independent and its energy to Tc ratio is nearly constant (2D/kBTc;5). Moreover,
the signal at the B1g channel is completely smeared out when nonmagnetic Zn21 impurities are present. These
results are discussed in terms of the current models of Devereaux et al., Venturini et al., and Zeyher and Greco.
DOI: 10.1103/PhysRevB.69.180501 PACS number~s!: 74.25.Gz, 74.72.2h, 78.30.2jThe phenomenon of high-Tc superconductivity in the cu-
prates has been related to an unconventional pairing
mechanism.1 It is widely accepted that this mechanism is
closely related to their normal-state properties, e.g., the non-
Fermi-liquid behavior,2 in spite of the lack of consensus
about the correct description of this state. The presence of
fluctuations, such as spin, flux phases, stripes, or charge-
density waves ~CDW!, are additional complications3 and
many models considering one or more of these fluctuations
have been proposed. However, there is still a large amount of
experimental results that these models cannot explain ~see,
e.g., Secs. 5.4 and 6.4 of Refs. 1 and 2, respectively!. Among
these results we can mention the absence of a convincing
explanation for the electronic Raman scattering ~ERS! of
many cuprates in the superconducting state.
The redistribution of the ERS in the superconducting state
has been used to study the gap order parameter in many
superconductors, both conventional and unconventional,
such as Nb3Sn,4 cuprates,5 borocarbides,6 and, recently,
MgB2.7 In general, the ERS of the superconducting cuprates
presents two characteristic peaks seen in the B1g and A1g
1B2g channels in the superconducting phase. In the opti-
mally oxygen-doped crystals of YBa2Cu3O72d ~Y123! the
ERS shows the A1g peak stronger than the B1g counterpart.
Also, the maximum intensity of the A1g peak lies at a lower
energy than that of the B1g one.8 In the overdoped state, the
B1g peak shifts down converging approximately to the posi-
tion of the A1g peak8 while in the strongly underdoped re-
gime neither A1g nor B1g peak is observed.
The appearance of these peaks just below Tc suggests that
they may be related to the superconductivity, being inter-
preted as pair-breaking peaks in several works in the litera-
ture. Some reports9 have already shown that for a gap with
nodes and dx22y2 order parameter, the ERS efficiency obeys
the ;v3 and ;v power laws at low energies in the B1g and
A1g1B2g channels, respectively. Also, these works have pre-
dicted that the A1g peak should be weaker than the B1g com-
ponent with their maxima appearing at the same energy 2D .
In spite of the good agreement between the theory and the
experimentally observed power laws, the relative position
and intensity of the ERS peaks are in disagreement with the0163-1829/2004/69~18!/180501~4!/$22.50 69 1805theoretically expected results for the pair-breaking ERS re-
sponse. Hence, the origin of the A1g and B1g peaks remains
unclear.
In this communication we make an attempt to clarify this
question by means of ERS measurements in Y123 single
crystals doped with a small amount, 5%, of either magnetic
Ni21 ~Y123:Ni! or nonmagnetic Zn21 ~Y123:Zn! impurities
in the copper planes. It is known that substituting Cu by Zn
or Ni in Y123 preserves the oxygen doping level and the
crystal structure is only slightly modified.10,11 Moreover, the
nonmagnetic Zn21 impurities, instead of the magnetic Ni21
ones, restore significant spin fluctuations in the normal
state.10,11 Since the presence of impurities in the CuO2 planes
are known to induce a pair-breaking effect,10,11 the investi-
gation of the change in the electronic properties by introduc-
ing magnetic and nonmagnetic impurities can give important
insights into the open questions related to the superconduc-
tivity in the cuprates.
Single crystals of Y123, Y123:Ni, and Y123:Zn were pre-
pared as previously described.12 After thermal annealing, the
transition temperatures, measured by dc-magnetization, were
91, 76, and 72 K for the Y123, Y123:Ni, and Y123:Zn
samples, respectively. In terms of the oxygen level, all
samples are in the optimally doped state. The Raman mea-
surements were carried out using a triple spectrometer
equipped with a charge-coupled device detector. The spec-
trometer response was corrected by measuring the emission
of a tungsten lamp and comparing it with the emissivity of a
blackbody at same temperature. The 514.5 nm line of an Ar1
ion laser was used as excitation source. The laser power at
the sample was kept below 8 mW on a spot diameter of
about 50 mm. The samples were cooled in an exchange He
gas variable temperature cryostat, and measured in a near-
backscattering configuration on the ab plane. For the tetrag-
onal D4h point group, the choice of the (x8,x8) geometry
probes a combination of the A1g and B2g channels, while
choosing the (x8,y8) geometry couples to excitations in the
B1g channel. x8 (y8) denote axes rotated by 45° from the
crystallographic a(b) axes.
In Fig. 1 we present the Raman spectra in the A1g1B2g
channel at different temperatures for the Y123, Y123:Ni, and©2004 The American Physical Society01-1
RAPID COMMUNICATIONS
H. MARTINHO, A. A. MARTIN, C. RETTORI, AND C. T. LIN PHYSICAL REVIEW B 69, 180501~R! ~2004!Y123:Zn samples, corrected by the thermal Bose-Einstein
factor. In Fig. 1~a!, the spectrum for Y123 at 100 K displays
a flat background. Just below Tc;91 K the rearrangement of
the electronic background starts, resulting in a broad peak in
the spectral range between 200 and 400 cm21. The same
behavior is also found in Fig. 1~b! for Y123:Ni. However, in
this case the rearrangement of the ERS starts only below
50 K, producing a broad peak located in the same spectral
range as that for the pure sample. For Y123:Zn, Fig. 1~c!, the
gain of spectral weight in the superconducting state is also
present in the A1g1B2g channel; although it starts to appear
at 40 K (Tc;72 K), it is also located in the same spectral
range as for the other two samples.
In the B1g channel, Fig. 2, the rearrangement of the ERS
is also displayed for Y123 and Y123:Ni. For Y123, Fig. 2~a!,
it starts below 70 K and it appears in the 450–650 cm21
spectral range. For Y123:Ni, Fig. 2~b!, the broad peak first
appears below 60 K and it is also located in the
450–650 cm21 spectral range. Surprisingly, for Y123:Zn,
Fig. 2~c!, the rearrangement of the ERS is absent below Tc .
The only observed effect of lowering the temperature was
the broadening of ;3 cm21 of the B1g phonon at 330 cm21.
In order to determine the energy of the broad peaks ap-
pearing in the superconducting phase in A1g1B2g and B1g
channels, the pure ERS response function has been obtained
by subtracting the contribution of the phonons fitted to
Lorentzian or Fano profiles to the Bose-Einstein corrected
raw data. We follow the currently used method of ERS
analysis outlined by Boch in Ref. 13.
In Fig. 3 we present the pure ERS response for the A1g
1B2g channel at 8 and 100 K. At 8 K we found the A1g
response peaks around 320, 250, and 300 cm21 for Y123
~3a!, Y123:Ni ~3b!, and Y123:Zn ~3c!, respectively. We no-
FIG. 1. Temperature dependence of the Raman spectra in the
A1g1B2g channel showing the redistribution of the ERS below Tc
for ~a! Y123 with Tc591 K, ~b! Y123:Ni with Tc576 K, and ~c!
Y123:Zn with Tc572 K single crystals.18050tice that the A1g energy to Tc ratio \vA1g /kBTc is ;5.0 for
Y123, ;4.7 for Y123:Ni, and ;5.8 for Y123:Zn. As com-
mented above, at 100 K, the rearrangement of the ERS is
absent and the Raman spectra present no pronounced peak.
Figure 4 shows the pure ERS for the B1g channel at 8 and
100 K. The dramatic difference between the response of
Y123:Zn compared to the other crystals is evident. The peak
is absent in Y123:Zn but it appears centered around
480 cm21 in Y123 and Y123:Ni. The ratio \vB1g /kBTc is
FIG. 2. Temperature dependence of the polarized Raman spectra
in B1g channel for ~a! Y123, ~b! Y123:Ni, and ~c! Y123:Zn.
FIG. 3. Electronic Raman response at 8 K ~black lines! and
100 K ~gray lines! for ~a! Y123, ~b! Y123:Ni, and ~c! Y123:Zn
single crystals in A1g1B2g channel.1-2
RAPID COMMUNICATIONS
ORIGIN OF THE A1g AND B1g ELECTRONIC RAMAN . . . PHYSICAL REVIEW B 69, 180501~R! ~2004!;7.7 for Y123 and ;9.2 for Y123:Ni. Moreover, the ERS
spectrum in Y123:Zn is almost the same at 8 and 100 K
being also quite similar to those in Y123 and Y123:Ni above
Tc , except for a constant offset in Y123:Zn. The origin of
this offset is not clear.
The data of Figs. 3 and 4 indicate that the Zn substitution
affects the A1g1B2g and B1g channels in a different way.
While in the A1g1B2g channel the intensities of the peaks
are unaffected by the impurities, in the B1g channel the peak
is smeared out in the Zn-doped sample. The comparison be-
tween the B1g channel signals at 8 and 100 K in Y123:Zn
indicates that the ERS in the superconducting and normal
states are nearly the same. This unusual effect of Zn substi-
tution on the B1g Raman response is surprising and has not
been predicted by any theoretical model neither been ob-
served by other systematic comparative experimental work.
Another relevant result is the almost constant energy to Tc
ratio ;5 for the A1g peak for all samples. This value is in
agreement with previous values obtained for the A1g
peak14,15 and for the superconducting gap measured by elec-
tron tunneling spectroscopy in Y123.16
Venturini et al.17 developed a model suggesting that the
observed peak in the A1g1B2g channel is produced by col-
lective spin fluctuations, being a two-magnon Raman peak.
In the same model, the B1g peak is related to pair breaking.
They were able to fit the experimental Raman spectrum of
Bi2212 to their model and obtained the correct relative po-
sition of the A1g and B1g peaks.17 Moreover, Gallais et al.15
have shown that the A1g peak tracks the magnetic resonance
peak observed by inelastic neutron scattering10 at 40 meV in
Ni-substituted YBa2Cu3O6.95 . These authors have inter-
preted this fact as an evidence for the magnetic origin of the
A1g peak.
However, our results cannot be interpreted in terms of the
FIG. 4. Electronic Raman response at 8 K ~black lines! and
100 K ~gray lines! for ~a! Y123, ~b! Y123:Ni, and ~c! Y123:Zn in
the B1g channel.18050works of Venturini et al.17 and Gallais et al.15 The main rea-
son is the strong Zn-impurity dependence observed in the
B1g spectra. In the Venturini’s framework the B1g peak is
related to pair-breaking process with their maximum at 2D
energy. Thus, the complete smearing out of the B1g peak
observed in our experiments @see Fig. 4~c!# would imply that
2D→0 for the Zn-substituted crystal. However, Tc does not
go to zero in this system and, assuming the absence of any
anomalous behavior in the 2D/kBTc ratio, 2D cannot go to
zero. Furthermore, the \vA1g /kBTc ratio for the A1g peak
presents better agreement to the gap energy measured by
other groups ~see, e.g., Ref. 15! than the B1g one, indicating
that the A1g peak is a better candidate to pair breaking.
Another model, by Zeyher and Greco,18 used the super-
conducting model of Cappelluti and Zeyher19 to explain the
ERS in cuprates. The model of Cappelluti and Zeyher pro-
posed that the superconductivity in cuprates is originated by
the competition between the superconducting and the
d-CDW order parameters. Zeyher and Greco18 suggested that
the A1g and B1g peaks are originated by amplitude fluctua-
tions of the superconducting and d-CDW order parameters,
respectively. The d-CDW phase corresponds to a flux phase
where current flows around each CuO2 square alternatively
clockwise and counterclockwise20 giving rise to orbital anti-
ferromagnetism where the only interaction present in the or-
der parameter is the Heisenberg exchange coupling between
the Cu21 ions.18
As mentioned above, our experimental data indicate that
the A1g peak is related to pair breaking. In this sense, our
experimental ERS results give support to the Zeyher and
Greco’s theory. However, this theory does not include the
impurity effects on its formulation. Intuitively, both magnetic
and nonmagnetic impurities should affect in some extent the
orbital antiferromagnetism. It is interesting to mention that
Cappelluti and Zeyher21 have shown that the Zn impurities
do not have appreciable influence on the oxygen doping
phase diagram of the cuprates. Therefore, the theory to ex-
plain the subtle effect of impurities on the ERS of cuprates
needs more ingredients.
Nevertheless we can elaborate, at least qualitatively, about
the impurity effect on the B1g signal as follows. It is known
that the main interaction originating the d-CDW is the
Heisenberg coupling between the Cu21 spins.21 Thus, it is
reasonable to expect that the Cu21 (S51/2) substitution by
nonmagnetic Zn21 (S50) impurity would strongly affect
the long-range coherence of the orbital antiferromagnetism
and smear out the d-CDW order parameter fluctuations. This
may be consistent with the large depletion of Tc produced by
the presence of Zn21 impurities.10,11 On the other hand, the
magnetic Ni21 (S51) impurities are probably less effective
in smearing out the orbital antiferromagnetism order param-
eter fluctuations, notwithstanding also decreasing Tc . Be-
sides, as shown by Gupta and Gupta,22 the charge-density
redistribution due to the Ni21 ions is localized while the
Zn21 perform an extended perturbation. On these bases, one
might expect that the Zn21 ions would be more effective on
reducing the d-CDW order parameter fluctuations.1-3
RAPID COMMUNICATIONS
H. MARTINHO, A. A. MARTIN, C. RETTORI, AND C. T. LIN PHYSICAL REVIEW B 69, 180501~R! ~2004!In conclusion, our results show that the A1g ERS peak
presents a constant gap to Tc ratio ;5 regardless of the
presence of magnetic or nonmagnetic impurities. The B1g
ERS peak is smeared out in the Y123 when the Cu21 is
substituted by small amount of nonmagnetic Zn impurities
whereas the A1g1B2g spectra remain insensitive to both
kinds of impurities. These results are incompatible with the
models of Devereaux et al.9 and Venturini et al.17 and were
qualitatively discussed in terms of the Zeyher and Greco’s18
theory that relates the ERS in the A1g1B2g and B1g channels
to superconducting and d-CDW order parameters fluctua-
tions, respectively.18050However, it is clear that more theoretical work is needed
to explain the impurity effects on the ERS of cuprates and
that Zeyher and Greco’s theory should be extended to explic-
itly incorporate the impurities effects.
ACKNOWLEDGMENTS
This work was supported by the Brazilian Agencies CNPq
and FAPESP. We would like to thank A. Greco, P.G. Pag-
liuso, and R. L. Doretto for fruitful discussions.1 T. Moriya and K. Ueda, Adv. Phys. 49, 555 ~2000!.
2 A. Chubukov, D. Pinnes, and J. Schmalian, in The Physics of
Superconductors, edited by K. H. Bennermann and J. B. Ketter-
son ~Springer-Verlag, Berlin, 2003!.
3 V. Barzykin and D. Pines, Phys. Rev. B 52, 13 585 ~1995!; W.
Anderson, Science 235, 1196 ~1987!; M.U. Ubbens and P.A.
Lee, Phys. Rev. B 46, 8434 ~1992!; P.A. Lee and X.G. Wen,
Phys. Rev. Lett. 78, 4111 ~1997!; J.M. Tranquada et al., ibid. 78,
338 ~1997!; C. Castellani, C. Di Castro, and M. Grilli, Z. Phys.
B 103, 137 ~1997!.
4 S.B. Dierker, M.V. Klein, G.W. Webb, and Z. Fisk, Phys. Rev.
Lett. 50, 853 ~1983!.
5 M. Cardona, Physica C 317, 30 ~1999!.
6 I.S. Yang, M.V. Klein, S.L. Cooper, P.C. Canfield, B.K. Cho, and
S.I. Lee, Phys. Rev. B 62, 1291 ~2000!.
7 J.W. Quilty, S. Lee, A. Yamamoto, and S. Tajima, Phys. Rev. Lett.
88, 087001 ~2002!.
8 A.A. Martin, V.G. Hadjiev, C. Bernhard, T. Ruf, M. Cardona, and
T. Wolf, Phys. Status Solidi B 214, R21 ~1999!.
9 T.P. Devereaux and D. Einzel, Phys. Rev. B 51, 16 336 ~1995!;
T.P. Devereaux et al., ibid. 54, 12 523 ~1996!; T. Strohm and M.
Cardona, Solid State Commun. 9, 233 ~1997!; M. Krantz and M.
Cardona, J. Low Temp. Phys. 99, 205 ~1995!.
10 Y. Sidis, P. Bourges, H.F. Fong, B. Keimer, L.P. Regnault, J.
Bossy, A. Ivanov, B. Hennion, P. Gautier-Picard, G. Collin, D.L.Millius, and I.A. Aksay, Phys. Rev. Lett. 84, 5900 ~2000!.
11 H.F. Fong, P. Bourges, Y. Sidis, L.P. Regnault, J. Bossy, A.
Ivanov, D.L. Milius, I.A. Aksay, and B. Keimer, Phys. Rev. Lett.
82, 1939 ~1999!.
12 C.T. Lin, S.X. Li, A. Mackenzie, W. Zhou, P.D. Hunneyball, and
W.Y. Liang, Physica C 193, 129 ~1992!.
13 A. Boch, Ann. der Phys. 8, 441 ~1999!; A. Boch et al., Phys. Rev.
B 60, 3532 ~1999!.
14 T. Strohm and M. Cardona, Phys. Rev. B 55, 12 725 ~1997!; T.
Strohm, D. Hunzar, and M. Cardona, ibid. 58, 8839 ~1998!.
15 Y. Gallais, A. Sacuto, P. Bourges, Y. Sidis, A. Forget, and D.
Colson, Phys. Rev. Lett. 88, 177401 ~2002!.
16 J. Geerk, X.X. Xi, and G. Linker, Z. Phys. B 73, 329 ~1988!; M.
Gurvitch, J.M. Valles, A.M. Cucolo, R.C. Dynes, J.P. Garno,
L.F. Schneemeyer, and J.V. Wasczak, Phys. Rev. Lett. 63, 1008
~1989!; A. Fournel, I. Oujia, and I. Sorbier, Europhys. Lett. 6,
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18 R. Zeyher and A. Greco, Phys. Rev. Lett. 89, 177004 ~2002!.
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20 H.J. Schulz, Phys. Rev. B 39, 2940 ~1989!; Sudip Chakravarty,
R.B. Laughlin, Dirk K. Morr, and Chetan Nayak, ibid. 63,
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21 E. Cappelluti and R. Zeyher, Europhys. Lett. 49, 487 ~2000!.
22 Raju P. Gupta and Miche`le Gupta, Phys. Rev. B 59, 3381 ~1999!.1-4


Origin Of The A1g And B1g Electronic Raman Scattering Peaks In The Superconducting State Of Yba2cu3o 7-δ

Crossref

Origin of the
                    
                      
                        
                          
                            A

The electronic Raman scattering was investigated in optimally
 oxygen-doped YBa2Cu3O7-delta single crystals as well in crystals doped
 with nonmagnetic, Zn2+ and magnetic Ni2+ impurities. We found that the
 intensity of the A(1g) peak is impurity independent and its energy to
 T-c ratio is nearly constant (2Delta/k(B)T(c)similar to5). Moreover,
 the signal at the B-1g channel is completely smeared out when
 nonmagnetic Zn2+ impurities are present. These results are discussed in
 terms of the current models of Devereaux , Venturini , and Zeyher and
 Greco

Martinho, H.

Martin, A. A.

Rettori, C.

Lin, C. T.

Max Planck Society eDoc Server

Origin of the A1g and B1g electronic Raman scattering peaks in the superconducting state of YBa2Cu3O7-δ