Evidence for multiband superconductivity and charge density waves in Ni-doped ZrTe2

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We carried out a comprehensive study of the electronic, magnetic, and thermodynamic properties of Ni-doped ZrTe2. High quality Ni0.04ZrTe1.89 single crystals show a possible coexistence of charge density waves (CDW, TCDW ≈ 287 K) with superconductivity (Tc ≈ 4.1 K), which we report here for the first time. The temperature dependence of the lower (H) and upper (H) critical magnetic fields both deviate significantly from the behaviors expected in conventional single-gap s-wave superconductors. However, the behaviors of the normalized superfluid density ρs(T) and Hc2(T) can be described well using a two-gap model for the Fermi surface, in a manner consistent with conventional multiband superconductivity. Electrical resistivity and specific heat measurements show clear anomalies centered near 287 K consistent with a CDW phase transition. Additionally, electronic-structure calculations support the coexistence of electron-phonon multiband superconductivity and CDW order due to the compensated disconnected nature of the electron- and hole-pockets at the Fermi surface. Our electronic structure calculations also suggest that ZrTe2 could reach a non-trivial topological type-II Dirac semimetallic state. These findings highlight that Ni-doped ZrTe2 can be uniquely important for probing the coexistence of superconducting and CDW ground states in an electronic system with non-trivial topology.

In Journal of Alloys and Compounds