We demonstrate that the feedback effect from bosonic excitations on fermions, which in the past allowed one to verify the phononic mechanism of a conventional, s-wave superconductivity, may also allow one to experimentally detect the 'fingerprints' of the pairing mechanism in cuprates. We argue that for spin-mediated d-wave superconductivity, the fermionic spectral function, the density of states, the tunneling conductance through an insulating junction, and the optical conductivity are affected by the interaction with collective spin excitations, which below Tc are propagating, magnon-like quasiparticles with gap Δs. We show that the interaction with a propagating spin excitation gives rise to singularities at frequencies Δ+Δs for the spectral function and the density of states, and at 2Δ+Δs for tunneling and optical conductivities, where Δ is the maximum value of the d-wave gap. We further argue that recent optical measurements also allow one to detect subleading singularities at 4Δ and 2Δ+2Δs. We consider the experimental detection of these singularities as a strong evidence in favor of the magnetic scenario for superconductivity in cuprates.
|Original language||English (US)|
|Number of pages||23|
|Journal||Journal of Electron Spectroscopy and Related Phenomena|
|State||Published - Jun 2001|
Bibliographical noteFunding Information:
It is our pleasure to thank A.M. Finkel’stein and D. Pines for stimulating discussions on numerous aspects of strong coupling effects in cuprates. We are also thankful to D. Basov, G. Blumberg, J.C. Campuzano, P. Coleman, L.P. Gor’kov, P. Johnson, R. Joynt, B. Keimer, D. Khveschenko, G. Kotliar, A. Millis, M. Norman, S. Sachdev, Q. Si, O. Tchernyshyov, A.Tsvelik, and J. Zasadzinski for useful conversations. We are also thankful to D. Basov and J. Zasadzinski for sharing their unpublished results with us. The research was supported by NSF DMR-9979749 (Ar. A and A. Ch.), and by the Ames Laboratory, operated for the US Department of Energy by Iowa State University under contract No. W-7405-Eng-82 (J.S).