Optical conductivity of the p-wave superconductor Sr2RuO4

Abstract

PACS. 74.20.-z -Theories and models of superconducting states. PACS. 74.25.Fy -Transport properties. PACS. 74.25.Gz -Optical properties.Abstract. -We study theoretically the optical conductivity of d-wave superconductors like in high temperature cuprates in the presence of impurities. We limit ourselves at T = 0K and focus on the frequency dependence of both σ1(ω) and ωσ2(ω) for ω 2∆. When the impurity scattering is in the unitary limit, we find a peak in σ1(ω) with ω/∆ ≃ 0.1 ∼ 0.5, which may account for the peak seen by Basov et al. in Zn-substituted Y BCO.Introduction. -Now d x 2 −y 2 -wave superconductivity is well established in both holedoped and electron-doped high temperature cuprate superconductors [1][2][3][4][5]. Further superconductivity in organic conductors in κ − (ET ) 2 salts appears to be of d-wave [6,7]. In spite of these developments, the optical conductivity in d-wave superconductors appears to be not well understood. For example Hirschfeld et al. [8] considered the microwave conductivity in d-wave superconductors in the presence of impurity in the unitary limit. However they were more interested in the temperature dependence rather than the frequency dependence. Similarly Sun and Maki [9] and Graf et al.[10] studied only some aspect of the optical conductivity. On the other hand, a recent infrared conductivity in Zn-substituted Y BCO exhibits a peak around ω/∆ ≃ 0.1 ∼ 0.2, which cannot be accounted for the above theories [11]. The object of this paper is to study the in plane optical conductivity focusing on the frequency dependence at T = 0K. As a model we take d-wave superconductors (with gap function ∆(k) = ∆ cos(2φ), φ is the in plane angle measured from the k x direction) in the presence of impurities in the unitary and Born limit. We assume that the former describes the Zn impurity while the latter the N i impurity [12]. In the following we summarize what we needed for the model, then we calculate σ 1 (ω) and ωσ 2 (ω) for impurities in the unitary and the Born limit for several impurity concentrations. Indeed, for the impurity in the unitary limit σ 1 (ω) develops a peak around ω/∆ ≃ 0.1 ∼ 0.2, somewhat similar to the one observed in Zn-substituted Y BCO. On the other hand, σ 1 (ω) in the Born limit develops a broad bump around ω/∆ ∼ 1.5.

Using Disorder to Identify Bogoliubov Fermi-Surface States

“…at zero temperature. Note that a non-zero DC-limit conductivity also appears in line-node superconductors, for example, d-wave superconductors [53,56,59,60], but it is not Drude-like in contrast to a BG-FS where σ 0 (r 0 ) ∝ 1/r 0 is manifested (See Inset of Fig. 2 (b)).…”