Thermal Conductivity In Near-nodal Superconductors

Thermal conductivity of superconductors reflects the properties of quasiparticle excitation.And assist us in judging the energy gap structure of superconductors.In d wave superconductors,the minimum energy gap is zero,and its thermal conductivity κ/T is a universal quantity independent of quasiparticle scattering rate..In near-nodal superconductors with non-zero energy gap minimum and far less than the maximum,what is the thermal conductivity behavior of the system?Here we investigate analytically the behavior of the thermal conductivity for any superconductors with near-nodes in the gap function.Here we show that in near-nodal superconductors,the thermal conductivity obeys a two-parameter scaling law,and can develop super-universal behavior if the temperature is about a half of the gap minimum.On the other hand,when the temperature is fixed at about one quarter of the gap minimum,the thermal conductivity can develop a dip versus the scattering rate,which is in excellent agreement with the behavior of the experimental thermal conductivtiy in Sr2Ru04.The excellent agreement between theory and experiment suggests that instead of implying nodal d wave pairing,the nodal-like feature in the experimental thermal conductivity actually implies near-nodes in the highly anisotropic p+ip’ wave gap function.In the first two chapters,the research motivation and related theoretical background are introduced in detail,including the introduction of superconducting gap symmetry,theoretical knowledge of thermal transport properties and the universal behavior of thermal conductivity.In the third part of this paper,we calculate the thermal conductivity of nodal and near-nodal superconductors.T The fourth part is the presentation and discussion of the calculation results.In the fifth chapter,the full text is summarized.