Field-induced quasiparticle excitations in novel type II superconductors

Abstract

We show that the field dependence of the magnetic penetration depth ($\lambda$), for which muon spin rotation ($\mu$SR) is an excellent microscopic probe, provides useful information on the degree of anisotropy for the superconducting order parameter. In type II superconductors associated with anisotropic order parameters, $\lambda$ is sensitive to the quasiparticle excitation induced by the Doppler shift due to a supercurrent around magnetic vortices. The presence of such low-energy excitations manifests itself in the non-zero slope of $\lambda$ against an external magnetic field. We review recent results on the field dependence of $\lambda$ obtained from the application of $\mu$SR to novel superconductors that exhibit unconventional characters associated with the anisotropic order parameter.

24 pages, 9 figures, submitted to J. Phys.: Cond. Matt. (muSR Special Issue)

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• SrPt${}_3$P: two-band single-gap superconductor
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• Penetration depth, multiband superconductivity, and absence of muon-induced perturbation in superconducting PrOs${}_4$Sb${}_{12}$
• On the interpretation of muon-spin-rotation experiments in the mixed state of type-II superconductors
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• The symmetry of the superconducting order parameter in PuCoGa${}_5$
• Muon spin rotation measurements of the superfluid density in fresh and aged superconducting PuCoGa${}_5$
• Two-Gap Time Reversal Symmetry Breaking Superconductivity in Non-Centrosymmetric LaNiC2
• Local spectroscopic evidence for a nodeless magnetic kagome superconductor CeRu${}_2$
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• Magnetic field-induced quasiparticle excitation in Nb3Sn: Evidence for anisotropic s-wave pairing
• Muon spin rotation study of the magnetic penetration depth in the intercalated graphite superconductor CaC6
• Comment on ``Muon-spin rotation studies of the superconducting properties of Mo_3Sb_7'', Phys.Rev.B 78, 172505 (2008)
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