Observation of a transverse Meissner effect in Cu sub(x) TiSe sub(2) single crystals

We report on local magnetization measurements showing the presence of an unexpectedly strong transverse Meissner effect in the superconducting Cu sub(x) TiSe sub(2) single crystals. We show that for tilted magnetic fields (H sub(a)) vortices remain aligned with the ab planes up to field H sub(k)H sub(p)/sin [theta] sub(H)(where [theta] sub(H) is the angle between the applied field and the ab plane and H sub(p) the first penetration field) and that for H sub(a)> H sub(k), the field dependence of the vortex direction [theta] sub(B)(H sub(a)) can be well described assuming that vortices remain partially locked in the planes forming a staircase structure of average direction [theta] sub(B)[theta] sub(H). These results indicate the existence of a strong modulation of the vortex core energy along the c axis but its origin remains unclear.