Impurity-induced quasiparticle transport and universal-limit Wiedemann-Franz violation ind-wave superconductors

Abstract

Due to the node structure of the gap in a d-wave superconductor, the presence of impurities generates a finite density of quasiparticle excitations at zero temperature. Since these impurity-induced quasiparticles are both generated and scattered by impurities, prior calculations indicate a universal limit (⍀→0, T→0) where the transport coefficients obtain scattering-independent values, depending only on the velocity anisotropy v f /v 2 . We improve upon prior results, including the contributions of vertex corrections and Fermi-liquid corrections in our calculations of universal-limit electrical, thermal, and spin conductivity. We find that while vertex corrections modify electrical conductivity and Fermi-liquid corrections renormalize both electrical and spin conductivity, only thermal conductivity maintains its universal value, independent of impurity scattering or Fermi-liquid interactions. Hence, low-temperature thermal conductivity measurements provide the most direct means of obtaining the velocity anisotropy for high-T c cuprate superconductors.

Renormalization of thermal conductivity of disordered d-wave superconductors by impurity-induced local moments

“…This result has been shown to be insensitive to vertex corrections due to anisotropic scattering [3]. Since v F is generally well-known, Eq.…”

Effect of controlled disorder on quasiparticle thermal transport inBi2Sr2CaCuNakamae1, Behnia2, Balicas3 et al. 2001Phys. Rev. B4312601View full textAdd to dashboardCite

“…And if yes, at which energy scale do they break down? To answer these questions, low-energy excitations in the superconducting state are under intense scrutiny [3,4].Low temperature thermal conductivity, κ, has proven to be an instructive probe of such excitations. A non-vanishing linear term in thermal conductivity of optimally-doped Y123 for T → 0 was the first solid evidence for a finite density states of nodal quasiparticles at zero energy [5].…”

“…And if yes, at which energy scale do they break down? To answer these questions, low-energy excitations in the superconducting state are under intense scrutiny [3,4].…”

Unconventional superconductivity in YNi2B2C

“…19 Here k 1 points in the direction of the node, k 2 is perpendicular to k 1 in the xy plane, and the gap velocity is v g = ∂∆/∂k 2 | node . In the vicinity of the jth node, the Green's function takes the form…”

“…We divide the volume of integration into four curved cylinder-shaped volumes, each centred around a line node on the Fermi surface 19 and perform the integration across the disk spanned by k 1 and k 2…”