title: Interplay of charge density wave and multiband superconductivity in 2H-PdxTaSe2.
abstract: 2H-TaSe2 has been one of unique transition metal dichalcogenides exhibiting several phase transitions due to a delicate balance among competing electronic ground states. An unusual metallic state at high-T is sequentially followed by an incommensurate charge density wave (ICDW) state at ≈122 K and a commensurate charge density wave (CCDW) state at ≈90 K, and superconductivity at TC ~ 0.14 K. Upon systematic intercalation of Pd ions into TaSe2, we find that CCDW order is destabilized more rapidly than ICDW to indicate a hidden quantum phase transition point at x ~ 0.09-0.10. Moreover, TC shows a dramatic enhancement up to 3.3 K at x = 0.08, ~24 times of TC in 2H-TaSe2, in proportional to the density of states N(EF). Investigations of upper critical fields Hc2 in single crystals reveal evidences of multiband superconductivity as temperature-dependent anisotropy factor γH = , quasi-linear increase of , and an upward, positive-curvature in near TC. Furthermore, analysis of temperature-dependent electronic specific heat corroborates the presence of multiple superconducting gaps. Based on above findings and electronic phase diagram vs x, we propose that the increase of N(EF) and effective electron-phonon coupling in the vicinity of CDW quantum phase transition should be a key to the large enhancement of TC in PdxTaSe2.
authors.affiliation: Center for Novel States of Complex Materials Research and Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: D
authors.initials: D
authors.lastname: Bhoi
authors.affiliation: Center for Novel States of Complex Materials Research and Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: S
authors.initials: S
authors.lastname: Khim
authors.affiliation: Center for Novel States of Complex Materials Research and Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: W
authors.initials: W
authors.lastname: Nam
authors.affiliation: Center for Novel States of Complex Materials Research and Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: B S
authors.initials: BS
authors.lastname: Lee
authors.affiliation: Center for Novel States of Complex Materials Research and Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: Chanhee
authors.initials: C
authors.lastname: Kim
authors.affiliation: Center for Novel States of Complex Materials Research and Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: B-G
authors.initials: BG
authors.lastname: Jeon
authors.affiliation: Center for Novel States of Complex Materials Research and Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: B H
authors.initials: BH
authors.lastname: Min
authors.affiliation: Center for Novel States of Complex Materials Research and Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: S
authors.initials: S
authors.lastname: Park
authors.affiliation: Center for Novel States of Complex Materials Research and Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: Kee Hoon
authors.initials: KH
authors.lastname: Kim