Electronic Raman scattering in a multiband model for cuprate superconductors

Abstract

Charge-charge, current-current, and Raman correlation functions are derived in a consistent way using the unified response theory. The theory is based on the improved description of the conduction electron coupling to the external electromagnetic fields, distinguishing further the direct and indirect ͑assisted͒ scattering on the quasistatic disorder. The two scattering channels are distinguished in terms of the energy and momentum conservation laws. The theory is illustrated on the Emery three-band model for the normal state of the underdoped high-T c cuprates which includes the incoherent electron scattering on the disorder associated with the quasistatic fluctuations around the static antiferromagnetic ͑AF͒ ordering. It is shown, for the first time consistently, that the incoherent indirect processes dominate the low-frequency part of the Raman spectra, while the long-range screening which is dynamic removes the long-range forces in the A 1g channel. In the mid-infrared frequency range the coherent AF processes are dominant. In contrast to the nonresonant B 1g response, which is large by itself, the resonant interband transitions enhance both the A 1g and B 1g Raman spectra to comparable values, in good agreement with experimental observation. It is further argued that the AF correlations give rise to the mid-infrared peak in the B 1g Raman spectrum, accompanied by a similar peak in the optical conductivity. The doping behavior of these peaks is shown to be correlated with the linear doping dependence of the Hall number, as observed in all underdoped high-T c compounds.

Microwave and magnetotransport properties ofRuSr2RCu2O8(Požek1, Kupčić2, Dulčić3 et al. 2008Phys. Rev. B6100View full textAdd to dashboardCite

“…In the first approximation (the case of noninteracting magnetic impurities [20]) we can write Γ iσ (k) ≈ Γ i ± α i M z , where α i is a constant and M z is the total magnetization of the RuO 2 layer). Thus, in the Ru1212R systems, at temperatures well above T m , we have σ xy given by [26,27] [20]. According to Eq.…”

“…In the present analysis, the splitting between two holelike CuO 2 bands is neglected and the AFM fluctuations in the CuO 2 planes are taken into account [26]. This gives the effective concentration of charge carriers (holes) in the CuO 2 layers n Cu to be proportional to p (n Cu ≈ 2p/V 0 ) rather than to 1+p, and with the band mass close to the free electron mass.…”

“…In the presence of the magnetic background of Ru 5+ /Ru 4+ ions and external magnetic fields the conductivity tensor in question is given by [26,27] The first term in the off-diagonal component σ xy comes from the Lorentz force and is proportional to H (ω 0 is the cyclotron frequency). The second term, σ ex xy , includes all extraordinary contributions and is proportional to the magnetization of the Ru lattice, which means that the dependence on H is given in terms of the Brillouin function B S (gµ 0 βSH).…”

Multiband Responses in High-T c Cuprate Superconductors

“…Their residual interactions create a pseudogap instead of the true gap used above, which means that the quasiparticle scattering contribution to the resistivity is large, and has indeed the expected Fermi-liquid T 2 dependence in the single-plane mercury and underdoped YBCO compounds. The pseudogap scale ∆ P G is visible in the temperature dependence of the Hall number n H = 1/(ecR H ) as an activation term [13][14][15],…”

Damping effects in doped graphene: The relaxation-time approximation

“…(33), (35), and (36) leads to the relation known as the effective mass theorem. For example, for the contribution to γ LL αβ (k, k + ; 2) ≈ γ LL αβ (k; 2) which are diagonal in the polarization index α, we obtain [1,45] …”