We report on local magnetization measurements showing the presence of an unexpectedly strong transverse Meissner effect in the superconducting CuxTiSe2 single crystals. We show that for tilted magnetic fields (Ha) vortices remain aligned with the ab-planes up to field H k ∼ Hp/ sin θH (where θH is the angle between the applied field and the ab-plane and Hp the first penetration field) and that for Ha > H k , the field dependence of the vortex direction θB(Ha) can be well described assuming that vortices remain partially locked in the planes forming a staircase structure of average direction θB = θH. This results indicate the existence of a strong modulation of the vortex core energy along the c-axis but its origin remains unclear.
We present a detailed study of the phase diagram of copper intercalated TiSe2 single crystals, combining local Hall-probe magnetometry, tunnel diode oscillator technique (TDO), and specific heat and angle-resolved photoemission spectroscopy measurements. A series of the CuxTiSe2 samples from three different sources with various copper content x and superconducting critical temperatures Tc have been investigated. We first show that the vortex penetration mechanism is dominated by geometrical barriers enabling a precise determination of the lower critical field, Hc1. We then show that the temperature dependence of the superfluid density deduced from magnetic measurements (both Hc1 and TDO techniques) clearly suggests the existence of a small energy gap in the system, with a coupling strength 2∆s ∼ [2.4 − 2.8]kBTc, regardless of the copper content, in puzzling contradiction with specific heat measurements which can be well described by one single large gap 2∆ l ∼ [3.7 − 3.9]kBTc. Finally, our measurements reveal a non-trivial doping dependence of the condensation energy, which remains to be understood.
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