Two-band model of Raman scattering on electron-doped high-Tcsuperconductors

Abstract

We have analyzed the B1g and B2g Raman spectra of electron-doped cuprate superconductors Nd2−xCexCuO4 and Pr2−xCexCuO4 using a weakly coupled two-band model. One of these two bands is centered around (±π/2, ±π/2) and couples more strongly with the B2g mode, while the other is centered around (±π, 0) and (0, ±π) and couples more strongly with the B1g mode. This model explains in a natural way why the B2g Raman peak occurs at a higher frequency than the B1g one at optimal doping, and how these two peaks change with doping in agreement with experiments. The result thus supports that there are two kinds of quasiparticles in electron-doped cuprates and d x 2 −y 2 -wave superconductivity is driven by the holelike band and a proximity effect on the electronlike band.

Impurity effect in electron-doped high-T c superconductors

“…The entire LDOS is obtained as i i i r r r = +   . Before we present our numerical results, it is necessary to clarify that our present model is actually an effective two-band model in the presence of AF order, qualitatively consistent with the two-band model proposed by [5,6]. Without the impurity term and considering a uniform AF order, we can transform the Hamiltonian to momentum space.…”

“…Based on angle-resolved photoemission experiments, it was revealed that there are two disconnected Fermi surface pockets [2,3], and thus, an effective two-band model may be required to describe electron-doped SC materials. Theoretically, several two-band models have indeed been proposed to account for low-energy properties [4][5][6][7]. Possible microscopic origins have been intensively discussed.…”

“…Possible microscopic origins have been intensively discussed. Based on the t−Jtype model, it was proposed that the magnetic band-folding effect induced by the magnetic correlation can account for this two-band feature [5,6]. Alternatively, the two-band feature can be explained based on the t U J -model, and the two energy bands arise from the upper Hubbard band and the Zhang-Rice singlet band [7].…”

Hole pocket–driven superconductivity and its universal features in the electron-doped cuprates

“…Given that the reduced resistive upper critical field for NCCO is largely independent of disorder type and amount, it is unlikely that the observed temperature dependence is dominated by disorder effects, but rather signifies a universal underlying characteristic of the doped CuO 2 planes of the electron-doped cuprates. Raman scattering experiments ( 45 , 46 ) also reveal that the coherent normal-state hole quasiparticles contribute to the superfluid density. Moreover, the superfluid response obtained from penetration depth measurements points to dual electron and hole contributions ( 39 , 47 ).…”

Transport anomalies and quantum criticality in electron-doped cuprate superconductors

“…The model requires different pairing strengths of electrons and holes in electron-doped cuprates, which is also used to ascribe the feature in Raman scattering on Nd 2−x Ce x CuO 4 and Pr 2−x Ce x CuO 4 [151].…”