Magnetic field-induced quasiparticle excitation in NbSn; Evidence for anisotropic -wave pairing

Kadono, Ryosuke*; Sato, Koki*; Koda, Akihiro*; Nagata, Takashi*; Furukawa, Hazuki*; Suzuki, Junichi; Matsuda, Masaaki; Oishi, Kazuki; Higemoto, Wataru  ; Kuroiwa, Sogo*; Takagiwa, Hiroyuki*; Akimitsu, Jun*

The response of vortex state to the magnetic field in NbSn is probed using muon spin rotation and small-angle neutron scattering. A transformation of vortex structure between hexagonal and squared lattice is observed over a relatively low field range of 2-3T. The gradual increase of the magnetic penetration depth with increasing field provides microscopic evidence for anisotropic (or multigapped) -wave pairing suggested by the Raman scattering experiment. This result renders need for careful examination on the difference of electronic properties between NbSn and VSi.