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

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, T-CDW = 287 K) with superconductivity (T-c = 4.1 K), which we report here for the first time. The temperature dependence of the lower (H-c1) and upper (H-c2) critical magnetic fields both deviate sig-nificantly from the behaviors expected in conventional single-gap s-wave superconductors. However, the behaviors of the normalized superfluid density rho s(T) and H-c2(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. (c) 2022 Elsevier B.V. All rights reserved.