Electronic Raman scattering in disorderedBi2Sr2Ca(

O. V. Misochko¹,

G. D. Gu²

Abstract

Electronic Raman scattering has been studied in single-crystal Bi 2 Sr 2 Ca(Cu 1Ϫx Fe y ) 2 O ␦ for different Fe concentrations. The 2⌬ peak positions of the B 1g and A 1g channels in the superconducting state are only slightly affected by impurity scattering with the ratio B1g / A1g unchanged. There is also no low-frequency threshold at any impurity concentration. These two features are consistent with unconventional pairing. However, the crossover scale to a cubic dependence in the B 1g channel, contrary to the d-pairing expectations, decreases with increasing Fe concentrations.

Interplay between the A1g electronic Raman scattering peak and the neutron magnetic resonance

“…: this is in clear contradiction to all the experiments, most studies showing the magnitude of the A 1g peak being even larger than the B 1g one[1,2,[16][17][18][19].…”

Condensation, excitation, pairing, and superfluid density in high-Tc superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

“…6(b), we plot T c versus the energy of this mode ω res , determined by neutron scattering for various cuprate systems [15][16][17][18]. We also include the peak energy ω A1g of the A1 g mode observed in Raman scattering [19][20][21][22], which closely follows the resonance mode energy. We see an impressive linear dependence of T c on ω res and ω A1g for wide variety of cuprates.…”

“…4 He observed by neutron scattering [60]. (b) The plot of Tc versus energy of the roton minimum of bulk superfluid 4 He (values for both axes multiplied by a factor 60) measured under applied pressures [61], compared with the relationship seen in HTSC systems for the energies of the neutron resonance mode at (π, π) [15][16][17][18] and the Raman A1g mode [19][20][21][22]. Also included are the neutron energy transfers at the (π ± δ, π) point in YBCO [17] and LSCO [62].…”

“…They include: 1) scanning tunnelling microscope results which confirmed the "swiss-cheese" like situation in Zn doped cuprates [9], and further established spontaneous formation of spatial heterogeneity in the superconducting state in a wide range of doping levels even without impurity substitution [10,11]; 2) highfrequency conductivity measurements of n s /m * , which showed a frequency-dependent "dynamic" response remaining above T c and provided the first direct evidence for a wide range of superconducting phase fluctuations in the normal state [12]; 3) the Nernst effect measurements which obtained further evidence for the dynamic superconducting response above T c , and mapped out the region of this response as a function of external field H, temperature T , and the doping concentration x [13,14]; 4) neutron scattering studies which established that the "41 meV magnetic resonance mode", first found in YBCO [15], is generic to many of the cuprate systems, and that the mode energy accurately scales with T c [16][17][18]; 5) Raman scattering studies which obtained the response in the A1 g mode at T → 0 whose energy precisely follows that of the neutron resonance peak [19][20][21][22]; and 6) a sharp "coherence peak" which appears in the antinodal response of ARPES studies, with the intensity proportional to the superfluid density [23].…”

Pairing symmetry and localization probed by electronic Raman scattering in disordered high-Tcsuperconductors

“…The independence of disorder for the polarization dependence has been reported for Fe-doped Bi2212. 16 However, apart from unchanged ratio of the peak frequencies in different symmetry channels, the experimental check of Devereaux's theory showed that a low-frequency portion of the spectrum, as a function of disorder, follows the behavior expected for an s wave. Namely, the spectral weight of the low-frequency portion of the spectra appeared to shift to lower rather than to higher frequencies.…”