Anomalous vortex state of superconducting ${\mathrm{LuNi}}_2{\mathrm{B}}_2\mathrm{C}$

Muon spin rotation has been used to investigate the magnetic-field distribution in the vortex state of superconducting ${\mathrm{LuNi}}_2{\mathrm{B}}_2\mathrm{C}$ ${(T}_c\approx 16\hspace{0.5em}\mathrm{K}).\mathrm{}$ Data for the magnetic field range ${0.06H}_{c2\mathrm{}}\lesssim H\lesssim {0.23H}_{c2\mathrm{}}$ are fitted to a nonlocal London model. The temperature dependence of the vortex core radius shows a clear Kramer-Pesch effect due to depopulation of bound states within the cores. Also, the penetration depth and core radius vary substantially with applied magnetic field, suggesting the presence of anomalous field-induced quasiparticles and vortex-vortex interactions.