Unconventional superconductivity observed with Raman spectroscopy in p- and n-type cuprates C. Kendziora a, * , B. Nachumi a , P. Fournier b , Z.Y. Li c , R.L. Greene c , D.G. Hinks d a Materials Science and Technology Division, Naval Research Laboratory, Code 6653, Washington, DC 20375, USA b Department of Physics, University of Sherbrooke, Quebec J1K 2R1, Canada c Department of Physics, Center for Superconductivity Research, University of Maryland, College Park, MD 20742, USA d Materials Sciences Division, Argonne National Laboratory, Argonne, IL 60439, USA Abstract We study the electronic Raman spectra of p- and n-type cuprates. In particular, we study the electronic continuum andtheenergyofthe2D peaksthatformbelow T c asafunctionofphotonpolarizationsymmetrywithinthecrystal).In the present work we discuss heavily overdoped Bi 2 Sr 2 CaCu 2 O 8d T c  54 K) where the electronic continuum and energy gap are dominated by excitations of B 1g symmetry. We compare and contrast this with n-type crystals of Nd 1:85 Ce 0:15 CuO 4d T c  21K)andPr 1:85 Ce 0:15 CuO 4d T c  22 K), where the superconducting 2D peaks are strongest inB 2g symmetry. All three samples show 2D max  4:5k B T c .Wediscussourresultsusingredk  647, 700 nm) excitation wavelengthsinthecontextofearlierstudiesperformedusinghigherenergygreenk  514:5nm)andbluek  476,488 nm) lasers. Published by Elsevier Science B.V. Keywords: Superconductivity; Raman spectroscopy; p-Type cuprates; n-Type cuprates; d-Wave As is well documented in the Raman literature, most cuprates exhibit clear 2D peaks indicating the size of the energy gap below T c . It is also generally found that the energy of the gap depends upon the polarizations of incident and scattered light, and therefore upon the symmetry within the crystal and ultimately upon the wave vector k [1]. Here we describe polarized Raman scattering from the electronic continuum for both p- and n-type cup- rate superconductors. For the p-type we concen- trate on the two-layer Bi 2 Sr 2 CaCu 2 O 8d Bi2212) because of its ease in cleaving along the a±b face andbecauseitispossibletoadjustthedopinglevel over a wide range with oxygen anneals. In this manuscriptwewilldealexclusivelywiththeheavily overdoped range of the Bi2212 system. For the n-type, we have measured two members of the single-layer cuprates with T 0 structure, Nd 1:85 Ce 0:15 - CuO 4d NCCO) T c  21 K) and Pr 1:85 Ce 0:15 - CuO 4d PCCO) T c  22 K). It is much harder to adjust the doping level in this class of crystals, and we concentrate on nearly optimally doped versions of each. The present spectra were all measured using red laser excitation. One advantage of this longer wavelength is increased instrumental resolution. Physica C 364±365 2001) 541±544 www.elsevier.com/locate/physc * Corresponding author. Tel.: +1-202-767-2414; fax: +1-202- 767-6980. E-mail address: kendziora@nrl.navy.mil C. Kendziora). 0921-4534/01/$ - see front matter Published by Elsevier Science B.V. PII:S0921-453401)00847-4