Temperature-dependent spectral function of a Kondo impurity in an s-wave superconductor

Chenrong Liu; Yixuan Huang; Yan Chen; C. S. Ting

doi:10.1103/PhysRevB.99.174502

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Temperature-dependent spectral function of a Kondo impurity in an s-wave superconductor

Chenrong Liu, Yixuan Huang, Yan Chen, C. S. Ting

DOI 10.1103/PhysRevB.99.174502 · Physical Review B

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Abstract

Using the numerical renormalization group method, the effect due to a Kondo impurity in an s-wave superconductor is examined at finite temperature T. The T behaviors of the spectral function and the magnetic moment at the impurity site are calculated. At T=0, the spin due to the impurity is in a singlet state when the ratio between the Kondo temperature Tk and the superconducting gap Δ(0) is larger than 0.26. Otherwise, the spin of the impurity is in a doublet state. We show that the separation of the double Yu-Shiba-Rusinov peaks in the spectral function shrinks as T increases if Tk/Δ(0)<0.26, while it expands if Tk/Δ(0)>0.26 and Δ(0) remains constant. These features could be measured by experiments and thus provide a unique way to determine whether the spin of the single Kondo impurity is in the singlet or doublet state at zero temperature.